Gordon Brown has been campaigning with Ken Livingstone ahead of London's mayoral elections.
The prime minister and Labour's mayoral candidate visited a Sikh temple in east London for the Vaisakhi new year celebrations on Monday.
Brown said: "Ken Livingstone has been a mayor who has, with great innovation, great determination and great support right across London, invested more in policing and protecting the people of our community than any local authority or any local leader before him."
Setting out a new "golden rule", the prime minister commended the Sikh community for its "values of tolerance, of equality, of justice, of treating people with fairness, values that uphold our religious and spiritual views".
"Treating others as you would like to be treated yourself is a rule that I believe has got relevance to every community in this country, building tolerance, building justice, building equality and building fairness," he said.
Livingstone said the government had "poured resources" into London, adding: "I say thank you to the prime minister.
"He's given me a vast amount more to do. All I require now is that you put me back to get on with the work. London has been given a chance it hasn't had for 30 years. Let's not see it squandered and wasted."
Contest
The contest between Livingstone and Conservative Boris Johnson is expected to be very close, with an Ipsos MORI poll for the Observer on Sunday putting the Tories on 51 per cent and Labour on 49 per cent.
Speaking earlier, the mayor said: "Every Londoner can now be sure their vote will count in this election - all polls show the race neck-and-neck.
"The choice is clear on May 1. London can vote to continue to move forward further as one of the world's most forward-looking and progressive cities, or it can retreat into a narrow, backward-looking, Conservative London under Boris Johnson."
Livingstone also released the names of 20 prominent figures in entertainment, the arts, and the environmental movement who are supporting him in his bid for a third term.
However, Johnson's campaign accused him of focusing on celebrities and not policies.
"On a day when Boris Johnson is meeting shopkeepers that have been robbed several times in this city, the mayor chooses to focus on people who make the gossip pages and not the news pages," a spokesman said.
"Ken has said this election is not 'Celebrity Big Brother', yet clearly he is now trying to cover up for his lack of new ideas."
Launching his business and skills manifesto, Johnson pledged to cut the annual £1.4bn cost of crime to the capital's businesses.
"These are the new ideas and fresh thinking that London needs," he said. "Ken Livingstone has been quiet on this issue for too long. It is time that London had a mayor who will make the changes that will keep business in the capital booming."
