Election watchdog inquiry over Lee Rigby ballot slogan
The Electoral Commission is facing a parliamentary inquiry in to how it let the name of murdered soldier Lee Rigby be used for political purposes.
The commission allowed the group Britain First to use the description "Remember Lee Rigby" on ballot papers in Wales for May's Euro elections.
House of Commons Speaker John Bercow has now been asked to intervene.
The commission said it has apologised to Fusilier Rigby's family and is deeply sorry for the offence caused.
But the elections watchdog says it is too late for ballot papers to be changed in time for the vote on 22 May.
Mr Bercow is chair of the Speaker's Committee overseeing the work of the Electoral Commission.
Now, the Cabinet Office Minister Greg Clark has written to Mr Bercow requesting that the error is investigated swiftly to ensure steps are taken to prevent "such a mistake ever happening again".
"Parliament has put the powers on the registration of political parties and the descriptions they use in the hands of the Electoral Commission," said Mr Clark.
"I have spoken to the chair of the commission, and the commission has acknowledged that it was a grave error to allow this wording to appear."
Britain First, which describes itself as a "patriotic political party and street defence organisation" is fielding four candidates in Wales.
The soldier slogan will only appear on ballot papers in Wales, as the party is not fielding any candidates in the Euro elections in England, while in Scotland it has chosen to use another description for itself.
In a statement, the commission said: "We have only just realised this mistake and are issuing this statement now that we have spoken to Lee Rigby's family."
Electoral Commission chair Jenny Watson added: "The Electoral Commission is deeply sorry for the offence that has been caused and I have apologised to Lee Rigby's family.
"We are particularly sorry at the pain that this will cause them, particularly since polling day falls on the first anniversary of Drummer Rigby's murder.
"The party description "Remember Lee Rigby" that was registered for use at the European Elections in May by Britain First should never have been permitted.
"We are sorry that the decision we made means that voters in Wales will now see the description on the ballot paper when they vote.
"We have looked carefully at what can be done to stop this from happening and we greatly regret that we have not found a way for the ballot papers to be changed."
The commission said the description will be removed from use in future elections.
Fusilier Rigby, from Middleton, Greater Manchester, was murdered as he returned to his barracks in Woolwich, south-east London on 22 May 2013. He died of multiple cut and stab wounds.
Two men, Michael Adebolajo, 29, and Michael Adebowale, 22, were found guilty of his "barbaric" murder after a trial at the Old Bailey.
Adebolajo was given a whole-life term - which he is appealing against - and Adebowale a minimum of 45 years in jail.
Britain First was registered as a political party in January this year.
A list of all candidates and parties standing in the European Parliament elections on Thursday 22, May, is available here.