Faced with the choice of hosting The Apprentice or taking on Barack Obama in next year's election, Donald Trump opted to stick with his television programme.

The multimillionaire has formally announced he will not be joining the small band of candidates seeking the Republican nomination for the White House race.

Few US political commentators took his campaign seriously and many suggested he was only in it for the publicity.

In a statement, he said: "After considerable deliberation and reflection, I have decided not to pursue the office of the presidency. This decision does not come easily or without regret, especially when my potential candidacy continues to be validated by ranking at the top of the Republican contenders in polls across the country."

Modesty is not a Trump characteristic and this is reflected in his statement. "I maintain the strong conviction that if I were to run, I would be able to win the primary and, ultimately, the general election."

He added: "I have spent the past several months unofficially campaigning and recognise that running for public office cannot be done half-heartedly. Ultimately, however, business is my greatest passion and I am not ready to leave the private sector."

The decision comes after the businessman was repeatedly trounced by Obama last month over the "birther" issue. Trump took doubts about Obama's birthplace from the fringes of American politics to the mainstream, but the president undercut him by publishing the long form of his birth certificate, proving he had been born in the US. Obama humiliated Trump a few days later with a series of jokes at his expense at the White House correspondents' dinner, with the businessman present.

In spite of Trump's claims about being frontrunner in the polls, one published on Monday by the Politico website and George Washington University showed 71% of those surveyed thought he had no chance of becoming president.

Trump went through the motions of being a Republican contender, making speeches in key early states such as New Hampshire, and for a short time seemed in tune with the public mood. But he offered little in the way of policies and senior Republicans viewed his candidacy, with its emphasis on issues such as Obama's birthplace, as an irritating distraction.

The field of declared Republicans so far is small and has failed to generate much excitement. Mike Huckabee, the former governor of Arkansas, who had a good run in 2008 in spite of a lack of funds, announced on Saturday that he would not be standing next year. Some Republicans see Obama as too tough a candidate and prefer to wait until 2016.

Sarah Palin, who would bring excitement to the race, has not yet said whether she will seek the Republican nomination. After a quiet few weeks, she re-ignited interest on Monday when she sent out a fundraising mail shot in South Carolina, one of the key states in the battle for the Republican nomination.