Ed Miliband has been warned by a leading political scientist that it would be short-sighted not to keep lines of communication open to the Liberal Democrats, because of the strong likelihood of a hung parliament after the next election.

The warning from John Curtice is published in Juncture, the journal of the influential left-of-centre thinktank the IPPR, and reflects views of some of its senior staff.

The issue of Lib Dem-Labour relations is currently rearing its head over Lords reform, and the extent to which Labour's dislike of the Liberal Democrats might motivate opposition MPs to block a measure that is seen as critical to Nick Clegg's credibility. The two parties are also at loggerheads over deficit reduction and party political funding.

The local elections saw Labour make big gains, often at the expense of the Liberal Democrats. The issue of future relations between the two parties is likely to be raised at a Progress conference on Saturday that Miliband is due to be address. The Labour leader, currently enjoying a poll lead, is likely to put forward a broad claim that Labour must become the party of change.

Curtice writes: "While Labour will undoubtedly want to win over and retain the votes of as many former Lib Dem voters as possible, it should not underestimate the potential value to the party of fostering good relations with the Liberal Democrats. The quality of the relationship between the two parties could well prove crucial to Labour's prospects of future power – before or after 2015."

He adds: "At the last three elections, on average, no less than 86 seats, or 13% of the total, were won by parties other than Labour and the Conservatives. In contrast, over the course of the seven elections between 1950 and 1970, the average level of third-party representation was just 11 seats. Meanwhile, at the last three elections rather less than one in five seats has been closely fought between Labour and the Conservatives, compared with well over a quarter in the 50s and 60s."

Citing work by the pollster Anthony Wells, Curtice suggests that the constituency boundary review will not make the position greatly different. His analysis shows that 16% of seats would have been marginal between Labour and the Conservatives, and third parties would still have won 12% of seats.

He also suggests that a collapse in the Lib Dem vote would benefit the Conservatives more than Labour. "A collapse results in no less than a 4.2-point drop in the target the Conservatives require for an overall majority, whereas the target Labour would need to meet falls by only half of that – 2.1 points.

"Although such support is less strongly concentrated in predominantly Conservative territory than it once was, the Conservatives would still be the main beneficiaries of any collapse in Lib Dem support – thereby making it much easier for the Tories in particular to win an overall majority."

Curtice, one of the most respected poll analysts in the UK, concludes: "So as deep as the Liberal Democrats' problems may be, Labour cannot afford simply to ignore them."

Looking at the period before 2015, he suggests that if Labour can win four Tory seats in byelections, it might be possible for Labour and the Lib Dems to form a stable coalition.

He also argues that a close Lib Dem-Labour relationship might constrain Cameron from forcing an early election, "if he felt there was any risk that rather than leading to an early election such a manoeuvre might instead precipitate coalition talks between Labour and the Liberal Democrats".

Curtice says one of the lessons of the coalition negotiations in 2010 is that when the chips are down, preparation and prior contacts matter. "In 2010, the Conservatives were ready and willing to do a deal, while previous contact had given Cameron and Clegg reason to believe they could work together.

"Labour, by contrast, was ill-prepared and internally divided on its willingness to strike a deal with the Liberal Democrats, while personal relations between key personnel in the two parties were poor. So while Labour will doubtless continue to mock and berate the Liberal Democrats in public, in private the party would be wise to keep the potential lines of communication open."