* FTSEurofirst up 4 pct on bailout of Fannie, Freddie
* Index on track for biggest 1-day gain since January
* Banks top gainers; only 7 stocks on FTSEurofirst decline
By Brian Gorman
LONDON, Sept 8 (Reuters) - European shares soared early on Monday, bouncing from last week's slump after the U.S. government seized control of major U.S. mortgage firms Fannie Mae <FNM.N> and Freddie Mac <FRE.N>.
At 0837 GMT, the FTSEurofirst 300 <FTEU3> was up 4 percent at 1,170.20. The index is on course for its biggest one-day gain since Jan. 24.
"This is such a huge story," said Arthur Van Slooten, strategist at Societe Generale. "Nothing else is making much of an impact today."
He added: "The credit spreads had been one of the major headwinds in the market. Now they should improve, and it's a huge relief. This will be a turning point for the market. But there's still some bad news to come in Europe, such as a recession."
European credit spreads enjoyed their sharpest rally since March, with the investment grade Markit iTraxx Europe index <ITEEU5Y=GF> more than 11 points tighter versus late on Friday.
The U.S. government on Sunday seized control of mortgage finance companies Fannie Mae and Freddie Mac, launching what could be its biggest bailout ever to support the U.S. housing market and ward off more global financial market turbulence.
The takeover plan makes it more explicit that debt issued by Fannie and Freddie will be backed by the U.S. government and curbed worries about possible losses among financial institutions and investors that hold such paper, analysts said.
Banks surged, with UBS <UBSN.VX> up 12 percent, BNP Paribas <BNPP.PA> up 8.9 percent, Credit Agricole <CAGR.PA> up 10.3 percent and HBOS <HBOS.L> up 12.7 percent.
The top 10 gainers in the index were banks.
Anglo Irish Bank <ANGL.I> was the biggest gainer, up 14.3 percent. Allied Irish Bank <ALBK.I> was up 12.8 percent. The DJ Stoxx European banking sector index <.SX7P> was up 7.6 percent.
Freddie Mac <FRE.F> shares in Frankfurt fell 50 percent, before being suspended.
DRUGS RARE LOSERS
Only seven shares on the index were lower. This included three drugs companies, as traders said investors were switching away from defensives. GlaxoSmithKline <GSK.L> was the worst performer, down 2.1 percent.
The FTSEurofirst 300 has fallen more than 22 percent so far this year, as banks suffered huge losses due to a global credit crisis and the economy slowed.
On Monday, economists at UBS cut their growth forecasts. The bank said it now expected growth of 1.2 percent in the eurozone in 2008, down from the previous estimate of 1.6 percent. For 2009, it forecasted 0.7 percent, a cut from 1.1 percent.
It said it continued to see substantial downside to bottom-line earnings estimates. However, it said the equity market was already pricing in the fall in earnings forecasts.
In other news, Associated British Foods <ABF.L> was up 1.3 percent, underperforming the market, after it said it expects discount fashion chain Primark to show underlying sales ahead 2 percent over the spring and summer months, and that it expects to meet its annual profit expectations. (Editing by Sue Thomas)