Ukip leader Nigel Farage dismissed Tony Blair as an "embarrassment" who should hold his tongue - and added he is opposed to Western military intervention in Iraq or Syria.
Mr Farage was commenting on the former PM's claims that lack of intervention in Syria is to blame for rise of Islamist insurgents in Iraq.
The Ukip leader said Mr Blair's "state of outright denial of the obvious consequences of his disastrous decision-making on Iraq is making increasingly uncomfortable viewing."
"In almost every country in which the West has intervened or even implied support for regime change, the situation has been made worse and not better," he said.
The UK's Electoral Commission says it has still not decided whether or not to take action against Nigel Farage over his failure to declare free use of an office.
Ukip have insisted Mr Farage made a declaration about the use - which constitutes a donation under electoral rules - to the EU authorities in Brussels after being advised to do so.
"We have not yet made a decision about whether any further action will be taken against Mr Farage for reporting the donations late," a spokesman said.
"We are continuing to review all of the necessary information supplied to us by Mr Farage and are considering it carefully."
Nigel Farage could be facing punishment from the elections watchdog over £200,000 worth of undeclared donations spanning a decade.
The Ukip leader had told EU authorities in Brussels that he has been receiving free use of a British office, but he did not inform the UK's Electoral Commission.
The British authorities were reportedly alerted to the issue by news reports in the run-up to the recent local and European elections.
A Ukip spokesman said Mr Farage had reported the use of the office to the Brussels authorities in line with "professional advice he had received at the time" and was "surprised" the Electoral Commission needed to be informed as well.
Nigel Farage said his "dream has become a reality" after Ukip topped the European parliament polls in England and Wales leaving the party with 23 MEPs.
He claimed Ukip was now the third party in British politics after the Liberal Democrats lost all but one of their MEPs in the election.
He added: "I think it is a political earthquake because I think the implications for Nick Clegg are very serious indeed, the implications for Ed Miliband are serious indeed and for David Cameron perhaps not quite as bad but that debate within his party is going to continue."
Nigel Farage hailed the "most extraordinary result in British politics for 100 years" as Ukip topped of the Euro polls in England and Wales.Read the full story ›
ITV News deputy political editor Chris Ship spoke to a jubilant Nigel Farage after his victory speech in Southampton.
The Ukip leader hailed a "massive result...right across the United Kingdom" and promised a "breakthrough coming tomorrow in Scotland."
He added that he would make the decision as to where to stand for a Westminster seat "before the summer recess" and confirmed it would be a constituency in the South East region.
Ukip leader Nigel Farage has been re-elected as an MEP in the South East region.
Nigel Farage has said Ukip is on track to win the European elections, describing it as being "an earthquake because never before in the history of British politics has a party seen to be an insurgent party ever topped the polls in a national election."
Six in ten people who voted Ukip in the European elections did so as a protest, according to polling from the influential Conservative, Lord Ashcroft.
Writing on the Conservative Home website, the peer said his survey of 4,000 voters found that 60% of Ukip voters had said they were voicing anger at the party they usually vote for or registering a more general protest.
However 80% of Ukip voters also said they thought Nigel Farage's party had the best policies on Europe.
The results of Thursday's European Parliament vote will be revealed tomorrow.