The race between the Conservatives and Labour has tightened as the general election approaches and voters increasingly expect a hung Parliament, according to the latest Populus poll for The Times.

The poll, undertaken over the weekend, shows that Labour has gained two points over the past month to 30 per cent, with the Conservatives slipping one point to 40 per cent. The Liberal Democrats are one point up at 20 per cent. Other parties are on 10 per cent, down two points.

These shifts are within the margin of error and are in line with other recent polls. Backing for the Tories has been stable since last summer at about 40 per cent. The main variations in the party’s lead have come from changes in Labour’s rating and shifts in support for the Lib Dems and other parties.

The poll shows that a big majority (70 per cent) believe that society is broken in Britain, with even more (73 per cent) believing that politics is broken. On a 0 to 10 scale of dissatisfaction to satisfaction, the political system rates lowest at 4.32. The performance of national government is rated at 4.42, while the NHS is at 6.51.

The Tories are now poised between a clear Commons majority and being just short of one in a hung Parliament. If the latest figures are translated into seats, according to the UK Polling Report ready reckoner, the Tories would be three seats short of an overall majority, but 75 MPs ahead of Labour.

If the Tories were one point higher and Labour one point lower, however, David Cameron would have an overall majority of 36.

These estimates assume a uniform national swing, or switch, of votes but, in practice, there are likely to be regional and local variations.

There is evidence, moreover, that the Tories may be doing better in their key target seats, which would mean an overall majority at this level of national support. A third of voters (33 per cent) now expect a hung Parliament, up from 22 per cent in early January. This is twice the level of last October. Forty-three per cent now expect an overall Tory majority, down from a peak of 57 per cent, four months ago. The proportion expecting the Tories to be the largest party, now 63 per cent, has varied less and the main shift has been between an overall majority and a hung Parliament.

The poll was conducted after the publication last Thursday of the names of MPs required to repay expenses cash, and the announcement on Friday of the prosecution of three MPs and one peer. There has been a sharp increase from 34 to 46 per cent since last April in the number thinking that their MP abuses the system of parliamentary expenses and allowances.

A third of voters (32 per cent) say that if their MP was among those required to repay money, they would vote against him or her, purely on that ground and regardless of which party he or she belonged to. Women and working-class voters are even more inclined to take this view: 63 per cent say they would take other issues, such as party policies and the qualities of other candidates, into account.

Recent media criticism of the Conservatives’ public spending plans has been followed by a four-point drop in the past month, to 43 per cent, in the number saying they trust Mr Cameron and George Osborne most to handle Britain’s economic problems. Trust in Gordon Brown and Alistair Darling has risen two points to 30 per cent — the narrowest Tory lead since March last year.

Economic optimism is also rising. Since December the number expecting the country as a whole to do well over the next year has risen from 35 to 37 per cent, while the number expecting it to do badly has dropped from 62 to 58 per cent. The net balance is the most favourable since April 2008. Just over half the public (51 per cent, up two points) now expect themselves and their families to do well over the next year, against 45 per cent badly (down two points since December).

Populus interviewed a random sample of 1,502 adults aged 18 plus between February 5 and 7. Interviews were conducted across the country and the results have been weighted to be representative of all adults. For more details go to www.populus.co.uk.