blair backs  pre-election budget  tony blair has backed chancellor gordon brown s pre-budget report amid opposition claims he was too bullish about the state of the uk economy.  in a speech in edinburgh  the prime minister said thursday s report reinforced stability and opportunity. and that would be central to labour s next election campaign  planning for which was already well advanced. mr brown earlier denied his economic forecasts were too optimistic - but refused to rule out future tax rises.  he told bbc radio 4 s today programme:  no politician should make the mistake that john major and his colleagues made in 1992 of saying no matter what the circumstances are  they can make all sorts of guarantees on every individual thing.   that is not what politicians should do  it would not be responsible to do.  mr brown insisted his spending plans were  affordable  and he could afford to be optimistic because britain was now a stable  low-inflation economy and house prices were now stabilising. mr blair praised his chancellor for his role in creating economic stability  which he said was the  cornerstone  of labour s programme.  in a speech at edinburgh s napier university  he said labour would publish over the next few months  a rich agenda for future policy in any possible third term .   in every area of work there is a detailed plan for the future  much clearer than those in 1997 or 2001. all of it fits together around common themes of opportunity  security and stability for all   mr blair said. in his pre-budget report  mr brown surprised some city experts by forecasting uk growth at between 3% and 3.5% for next year. many believe the figure is more likely to be under 3% - and fear tax rises or spending cuts  saying tax receipts have been overestimated. carl emmerson  from the institute for fiscal studies  told bbc news:  he thinks everything will come out in the wash and it will  in fact  be ok. we re not so sure.  david page  of investec securities  said:  his forecast that he will meet the golden rule with a margin of £8bn is way too optimistic.  it s going to take a significant turnaround in the economy to meet these targets.   conservative shadow chancellor oliver letwin said:  i can t find a single economic forecaster from the imf to the institute of fiscal studies who believes anything other than the chancellor has got a black hole in his finances.  in order to deal with that he will have to raise taxes after the next general election.  mr letwin accused the chancellor of using  fancy statistics  to hide public service failures. vincent cable  for the liberal democrats  called on mr brown to open up the government s books to the national audit office  to see if he had met his  golden rule .  it is very clear that there are some serious loose ends in government public spending   mr cable told mps.