Liberal Democrats in Liverpool Wavertree have sought advice from one of the city's top lawyers, Rex Makin, about an email sent to members of the Jewish community, among others, apparently claiming that the LibDems backed Liverpool Friends of Palestine.
The email alleged that a LibDem leaflet had been inserted into one from Liverpool Friends of Palestine and then pushed through doors in the constituency. This, it was claimed, showed that the Wavertree LibDems had colluded with the organisation.
The Palestine group's leaflet attacked Labour Friends of Israel and the Labour candidate Luciana Berger, LFI's director. It also asked people "not to vote" for Conservative and Liberal Democrat Friends of Israel.
But an angry Colin Eldridge, the LibDem candidate in Wavertree, denied any link with the pro-Palestine group.
"This is all dirty tricks," said Mr Eldridge. "Our supporters were outside a mosque on Friday handing out our leaflet at the same time as the Friends of Palestine group. Somebody has put the two together, photocopied them, spread them around and then said we were distributing both. When our supporters discovered the Friends of Palestine were there, they left."
Retiring Wavertree MP Jane Kennedy said that she had forwarded the e-mail to two journalists.
She said: "We were obviously appalled at what appeared to be happening and we could not let this go without comment."
Labour's Luciana Berger said: "If the LibDems believe that people should vote against Labour candidates because they are friends of Israel, they should have the honesty to say so, to Jewish as well as Muslim voters."