LONDON, Oct 20 (Reuters) - Britain's opposition Conservatives have stretched their lead over the ruling Labour Party to 17 points while optimism about the economy's prospects hit a 12-year high, pollsters Ipsos MORI said on Tuesday.
Such a big lead would put the Conservatives on course to return to power with a big parliamentary majority if repeated at a national election that Prime Minister Gordon Brown must call by next June.
In the telephone poll of 996 people, 43 percent said they would vote Conservative, up seven points from a similar poll last month.
Labour's score rose two points to 26 percent while the Liberal Democrats, who had pushed Labour into third place in last month's poll, fell back six points to 19 percent.
A deep recession, a scandal over politicians' expenses, Brown's unpopularity and voter fatigue with Labour after 12 years in power have slashed the party's support.
Polls in September and October, when British political parties hold their annual conferences, are often volatile as parties get a short-lived boost from basking in publicity or announcing popular policies.
Ipsos MORI said voting intentions had returned to the position they were in before the conference season.
The poll found both Brown and Conservative leader David Cameron's personal ratings had improved since last month. But less than a third of voters were satisfied with the way Brown was doing his job as prime minister.
Just under half were satisfied with Cameron's performance.
Even though the British economy is struggling to emerge from recession and the public finances suffered their worst six months on record between April and September, the poll found optimism about economic prospects continued to improve.
Some 44 percent of those polled thought the British economy would improve over the next year, while 23 percent thought it would get worse.
That produced a reading of +21 on Ipsos MORI's Economic Optimism Index, the highest since May 1997, the month that Labour came to power. (Reporting by Adrian Croft; Editing by Jon Hemming)