A leading cabinet member attempted to suggest that a Lib-Dem candidate was currently being prosecuted in court, but had failed to find out that the person in question had been acquitted of the offence nine years ago.
Councillor David Simmonds, deputy leader of Hillingdon Council (Con), posted a link to a nine-year-old news article on an internet chat site. The Gazette also received a fax last Wednesday from the Conservative group office.
Councillor Simmonds claims that he was simply 'given wrong information'.
The link concerned Yiewsley ward candidate Gay Brown, who was cleared of two charges relating to intimidating badly behaved children in a case which she says 'should never have made it to court'.
Ms Brown has, in the past, fought Tesco's plans for a store in Yiewsley, even speaking in parliament about the power of the supermarket.
Councillor Mike Cox, leader of the Liberal Democrats, said: "Gay Brown has worked tirelessly for the residents and traders of Yiewsley and to have inaccurate information dragged up after nine years is sickening. No wonder people get put off politics.
"Councillor Simmonds is paid an awful lot of money to look after the interests of children in Hillingdon.
"I hope he performs that task with more diligence than he does in trawling the internet for dirt on political opponents."
Councillor Simmonds is the cabinet member for education and children's services, and is paid £55,000 a year in allowances. He claimed an additional £2,000 in expenses last year.
Ms Brown, who is standing for the Liberal Democrats in Yiewsley at the forthcoming council elections, said: "It is mud slinging, plain and simple.
"I should take it as flattery that they think I have a chance of winning. To drag out something like this, which is irrelevant, is wrong. I have had five successful criminal records checks since.
"No wonder politics has so much bad publicity."
Councillor Simmonds was backtracking about the row on Monday.
He said: "I don't want to add anything more. I was led to believe the story was current and did not realise it had an old date.
"If it happened today it would be important but if it's ancient history, it's ancient history."
* Do you think a councillor should be engaging in this sort of activity, or is all fair in love and politics? Email firstname.lastname@example.org.