David Cameron says he wants to stay on as British prime minister until 2020, calling his agenda of reforms enough to keep him busy through another term.

The prime minister's remarks to the Sunday Telegraph newspaper come a day before he and Deputy Prime Minister Nick Clegg publish a midterm review of how their coalition government, formed in 2010, has fared.

Relations between Cameron's Conservative Party and Clegg's Liberal Democrats have become strained over disagreements on austerity measures, political reforms and other matters.

Cameron told the newspaper there was no turning back on policies such as allowing same-sex marriage or the protection of foreign-aid spending, which have been unpopular with his party's grass roots. He urged critics in his party to "stop complaining."

Calling his "enormous reform agenda" enough to "keep us all busy," Cameron said he wants to "fight the next election, win the next election and serve."

Britain's next general election is scheduled for 2015.