* Internal party critics fan leadership speculation
* Discontent driven by poll ratings, poor state of economy
* Senior party figures dismiss leadership talk as nonsense
* Cameron, more popular than own party, determined to stay
By Andrew Osborn
LONDON, March 15 Two senior members of British Prime Minister David Cameron's ruling Conservative party spoke out to calm growing talk of a leadership challenge against him on Friday, days before a closely watched budget.
Halfway through a five-year term, Cameron's Conservatives are trailing the opposition Labour party by 10 percent in the polls, the economy is stagnant, some lawmakers say they are unhappy with his leadership, and one of his ministers is being touted as a possible replacement.
But on Friday, two senior party figures insisted Cameron's leadership was not under threat ahead of a general election in 2015, dismissing media stories which have suggested others may be positioning themselves to usurp him.
"David Cameron is more popular than all of us ... more popular than all of the party in the country, which is a key point that lots of people do recognise," said Conservative Party Chairman Grant Shapps.
Talk of a leadership challenge was "for the birds and certainly not for today," he told political magazine The House.
London Mayor Boris Johnson, who has himself been tipped as a leadership candidate, agreed. "People need some sort of political drama so they're inventing one. I think it's complete nonsense," he told The Sun newspaper.
Cameron is going through a bruising time politically.
His party was beaten into third place in a vote for a parliamentary seat earlier this month, half of his party rebelled against him over a gay marriage law last month, he is at odds with his junior coalition partner on press regulation, and is being criticised for his ambiguous stance on an alcohol control law.
Most analysts believe the malcontents are in the minority and would have scant chance of unseating Cameron if they chose to try. No serious rivals have emerged, they say, and even most internal detractors think Cameron should remain leader.
But, as his finance minister, George Osborne, prepares for a budget on Wednesday that will give the Conservatives a chance to tip the political scales in their favour, Cameron's position remains the subject of almost weekly speculation.
This week, Theresa May, the home secretary or interior minister, delivered a speech that went well beyond her brief, prompting media speculation she was angling for Cameron's job.
Labour taunted Cameron over the speech in parliament as Conservative party strategists told MPs to curb their criticism of Cameron on social media and to decide if they were commentators or participants in the battle to win the next election.
Johnson said it was time for the party to unite.
"If ministers are setting out their stall now, it strikes me as being very odd," he said. "They should save their breath and cool their porridge. Put a sock in it and get on and back the Prime Minister."
In a party political TV broadcast earlier this week, Cameron shrugged off the speculation about his leadership as "rubbish".
"It's so vital that you look to the horizon and not tomorrow's headlines, because there is a sort of daily battle of this story and that event," he said. "It's all rubbish."
Several Conservative lawmakers disenchanted with his leadership have said they would judge him by five "key tests".
In their eyes, he has already failed two of them after his party lost a vote for a parliamentary seat in the constituency of Eastleigh earlier this month and the country lost its top-notch AAA credit rating in February.
Three tests remain: setting out a successful budget on Wednesday, avoiding a triple-dip recession, and performing reasonably well in local elections in May.