Tory support for Ukip pact narrowly trails that for another deal with Lib Dems in event of hung parliament next year

Nearly a third of Conservative voters would prefer their party to form a coalition with Nigel Farage's party rather than any other, according to a survey.

The figure of 30% support for a coalition with Ukip compares with 31% who would favour a continuation of the current partnership with Liberal Democrats in the event of a hung parliament in 2015.

The survey by TNS UK found that the Liberal Democrats were the favoured party of coalition for supporters of both the Conservatives (31%) and Labour (32%) if either party does not win an outright majority.

Lib Dem voters preferred a coalition with the Tories rather than Labour by a margin of 36% to 26%, with 13% saying the party should go into opposition rather than joining another coalition.

Tory voters' enthusiasm for a linkup with Nigel Farage's Eurosceptic party was not matched by Ukip voters, 39% of whom said any MPs they secured next May should remain refuse to join a coalition at Westminster. Another 24% said they should enter government with the Conservatives, 13% with Labour and 8% with the Lib Dems.

Among Labour voters, 27% said they preferred opposition to coalition. Among Conservatives the figure was lower at 16%. More than a quarter of Labour supporters (29%) said they did not know what Ed Miliband should do if he finds himself in coalition negotiations after the election.

The poll gave Labour a seven-point lead on 36%, to the Tories' 29%, with Ukip on 19% and the Liberal Democrats trailing on 7%. But despite Ukip's apparent advantage over the Lib Dems, the first-past-the-post electoral system is likely to deny the party any more than a handful of MPs.

Michelle Harrison, an executive at TNS, said it was questionable whether a Tory-Ukip coalition could be considered a viable option. "While it is perhaps no surprise that a sizeable number of Conservative supporters favour a coalition with Ukip, the probability of that being a viable option at the next election is open to question," she said.

The poll suggested that Lib Dem support was much softer than that for the other parties. Of those saying they would vote Lib Dem in 2015, 47% said they might change their minds over the coming nine months, compared to 34% of Ukip backers, 24% of those supporting the Tories and 22% of Labour voters.

David Cameron's offer to renegotiate Britain's membership of the EU may not sway many voters, according to the poll. It was placed 10th out of a list of 10 possible policy priorities, with just 5% of those questioned naming it as their top priority, against 28% who said it was their lowest.

Topping the list were reducing unemployment, where the Tories were rated the party most likely to deliver, and investing more in healthcare, where Labour were most trusted.

Just over a third (34%) of those questioned said the economy had improved over the last 12 months, against 14% who said it had got worse. Looking ahead, just 29% expected it to get better over the coming year, while 59% said it would stay the same and 11% that it would decline.

• TNS Omnibus interviewed 1,191 adults in Great Britain between 15 and 17 July.