Plot

Ali G unwittingly becomes a pawn in the Chancellor's plot to overthrow the Prime Minister of Great Britain. However, Ali is embraced by the nation as a voice of the youth, making the PM and his government more popular than ever.

Ali G (Sacha Baron Cohen) unwittingly becomes a pawn in evil Chancellor David Carlton's (Charles Dance) plot to overthrow the Prime Minister of Great Britain (Sir Michael Gambon). However, instead of bringing down the Prime Minister, Ali is embraced by the nation as the voice of youth and "realness", making the Prime Minister and his government more popular than ever.

Ali G (Sacha Baron Cohen) is the leader of Da West Staines Massiv, a fictional gang composed of a group of wannabe gangsters from Staines, a suburban town in north Surrey, to the west of London. Their chief rivals are Da East Staines Massiv. Da East and the Da West gangs engage in name calling, fat mother jokes (which Ali says is a result of a glandular problem), and street races which strictly adhere to the speed limits posted across town.

Ali is a pimp, but dreams of himself as the protector of the interests of prostitutes from other gangs who try to extort them. In his fantasy, Ali also faces off against the gang in a fire fight all by himself, and bullets cannot even touch him. Ali's most loyal gang member is Richard "Ricky C" Cunningham (Martin Freeman). Ali is going steady with "Me Julie" (Kellie Bright).

Ali and Da West Staines Massiv are heartbroken to learn that their beloved local leisure center, where they like to chill out and also where Ali teaches his "Keep it Real" classes, will be demolished by the local council. Ali teaches a class of toddlers about how they would die from an overdose of cocaine and calls them Batty Boys if they cry. Students are given badges for hot wiring, and advanced swearing.

Ali and his friends decide to protest this injustice. After he goes on a hunger strike and is spotted chained to some railings by the nefarious Chancellor of the Exchequer/Deputy Prime Minister David Carlton (Charles Dance), he is drawn into a world of seedy political intrigue, as the Deputy Prime Minister tries to use Ali as a tool to destroy the Prime Minister's credibility. The ruling party is dealing with low approval ratings and is accused of being out of touch with the youth of the country. Carlton was looking for a suitable candidate for the upcoming by-election in Staines, which is crucial to win for the Prime Minister.

Carlton visits Staines to look at the list of potential candidates when he spots Ali. Ali's shorts had been pulled down by the East Staines Massiv. Carlton calls Ali for a meeting, and Ali is instantly attracted to Carlton's secretary Kate (Rhona Mitra). Ali has been on the dole for 8 years and 3 months. Ali claims disability due to a DJ injury due to which he does not have full mobility on his main mixing finger. Carlton tells Ali that as an MP he could save the local leisure center. Carlton is betting that Ali will lose the election and this will create a vote of no confidence for the PM and he will be out. Carlton would thus be the next PM of the country. Ali has 2 weeks to loose 18,000 votes.

Ali is put forward as a candidate to be the next MP for Staines in a crucial by-election and manages to alienate most who cross his path, including feminists and the elderly. With one day to go, Ali was 8 points behind in the opinion polls. During a debate with his rival candidate, Ali tries to insult his rival by claiming that he "sucked off a horse". Unknown to Ali and the public, it turns out that the rival did indeed do such a thing, and trying to explain it away, he claims when he was out hunting with a friend he slipped, and his mouth landed on a horse's penis, which due to the mating season was erect. Ali wins the election in a landslide.

Although originally seeming out of his depth as a Member of Parliament, Ali's bizarre behavior and solutions seem to actually work. He visits a Customs checkpoint in Dover, as a delegate compiling a report, though all he does is steal confiscated pornography and drugs. Through ideas such as making more "relatable" education and selectively ensuring the immigration of attractive (or "fit") women into the UK, Ali becomes incredibly popular, meeting the Prime Minister's intentions and bringing his percentage lead in the polls up twenty two percent.

With this the Prime Minister offers to save Ali's John Nike Leisure Centre. First though, Ali accompanies the Prime Minister to a United Nations peace conference to avert war between the central African states of Chad and Burkina Faso. The USA and Russia back opposite countries and both threaten nuclear attacks. It gets to the point where World War III is almost declared when Ali sneaks into the catering area and puts an entire bag of marijuana, which he had stolen from Customs earlier, into the delegates' tea and orders that they be served it right away. He throws the empty bag into a nearby rubbish bin.

A side-effect is that the two opposing African presidents become allies (in fact they begin to kiss lovingly). The Prime Minister says that Ali has saved the world. However, Carlton's secretary Kate Hedges figures out what Ali has done and retrieves the empty marijuana bag (which has "Ali's stash. DO NOT NICK" written on the back), which she mails to the press.

Upon his return to the UK, Ali is forced to leave parliament. Before the Leisure Centre can be saved, a video emerges of Ali and his girlfriend having sex in the Prime Minister's bedroom at Checkers. As Ali was wearing items of the Prime Minister's clothing at the time, the media believe the video details the Prime Minister with a prostitute, forcing his resignation.

This results in Deputy Prime Minister David Carlton being made Prime Minister. Carlton, who despises Ali, orders the destruction of the aforementioned leisure center. He has also bought all available real estate in Staines in the knowledge that the town is to be destroyed to make way for a new terminal for Heathrow Airport, which will make him super wealthy.

After turning down an offer to have sex with Kate Hedges, in exchange for "keeping his mouth shut" about the videotape, Ali and the West Staines Massiv must race against time to find the master copy of the CCTV tape proving the former Prime Minister's innocence, extending the olive branch to all the gangs all over Staines and neighboring Berkshire (even to the East Staines Massiv) to help them break into the vaults and retrieve the said tape.

They do this successfully and manage to reinstate the original Prime Minister, save the Leisure Centre, and all live happily ever after when Ali is posted as the British ambassador to Jamaica. Staines is saved from destruction, with the reinstated Prime Minister declaring that Slough is to be destroyed instead.