Mr Alvarez and Mrs Fernandez Meijide had the grace to apologise, and the alliance, saying it would not takepartinadebate rescheduled for this week, tried to put the fiasco behind it.
On the eve of the 2001 election Mr Blair was accused of being "chicken" when he turned down the opportunity to takepartina planned debate between Britain's three main political parties.
Prof Bogdanor told Today presenter James Naughtie that retired members of the armed service "have every right to takepartin the political debate, " but added that former personnel "must not appear to align themselves with a political party, " particularly in the build up to a general election.