UPDATE 1-UK PM will not soften austerity despite IMF growth cut

(Adds quotes from Sky interview, context, details)

BIRMINGHAM, England, Oct 9 (Reuters) - British PrimeMinister David Cameron said on Tuesday he would not soften hisausterity programme with a "Plan B" of slower spending cutsafter the International Monetary Fund downgraded its growthforecasts for Britain.

The IMF cut its UK economic growth estimates on Monday,predicting the economy would shrink 0.4 percent this year beforegrowing by 1.1 percent in 2013. In July, the IMF had saidBritain's economy would grow 0.2 percent this year and 1.4percent in 2013.

The IMF also said Britain should delay some spending cutspencilled in for next year if growth turned out to be muchweaker than forecast, but Cameron said that did not mean hisConservative-led government should change its plans yet.

"What we need in Britain is not 'Plan B', which is moreborrowing. How can you borrow your way out of a debt crisis?"Cameron told Sky News.

"What we need is what I call 'Plan A+', we need to keep ourplans, difficult though they are to cut public spending and dealwith the deficit, but we need to add to that every measure thatbusiness has been asking for. And that's what we're doing."

"The IMF are not saying change course, they are saying stickto your plan unless things get dramatically worse," he said.

(Reporting by Matt Falloon; Editing by Alessandra Rizzo)