Grassroots Liberal Democrats would prefer to join forces with Labour after the next general election than support the Tories, according to a poll by a leading party website.

The poll of more than 600 members by the Lib Dem Voice website found greater support – by 55% to 18% – for a post-election alliance with Labour than for maintaining a pact with the Tories.

The poll found that 40% would like to form a coalition with the Labour party after the 2015 election. It found that 15% would prefer a "confidence and supply" arrangement with Labour in which the Lib Dems would not form a coalition with Labour but would agree to keep it in power by not voting against the budget or the Queen's speech.

The poll found much less support for a continuing Lib Dem alliance with the Tories. It found that 13% would support another coalition with the Tories and 5% would support a "confidence and supply" deal with the Tories. The poll found that 72% of members believed there would be a hung parliament in which no party had an overall majority.

Stephen Tall, the website's co-editor, wrote: "Tactically, it makes sense for the Lib Dems to want to choose Labour next time: it would show the party isn't simply an adjunct to the Tories but can work with both other major parties if that's how the public votes.

"On a principled basis, Labour's position on a range of big economic issues – tax-cuts for the low-paid, the 'mansion tax', ending universal benefits for wealthier pensioners – has moved towards the Lib Dems' in recent months.

"Personally, I'm very doubtful the Lib Dems will form a coalition with either party. I do not think the party will approve a second full coalition with the Conservatives: the party's 'triple lock' – which means any deal must be approved by large majorities by each of the parliamentary party, the elected federal executive and a special conference – will, almost certainly, prevent it."