The South Yorkshire MPs described Jane Collins’s application for immunity on the grounds of being a member of the European Parliament as an “absurd irony”.
As one of Yorkshire’s two UK Independence Party MEPs, Mrs Collins has been consistently critical of the EU and its institutions.
MPs Sir Kevin Barron, Sarah Champion and John Healey are claiming damages of £150,000 each over a speech Ms Collins made at the UKIP conference in Doncaster in 2014.
In a joint statement, the MPs said: “It is 18 months since we challenged the deeply damaging and totally baseless allegations Jane Collins made in a speech to the UKIP national conference.
“At every stage since then she’s tried to duck and delay the process of justice.
“The judge today was set to decide on the damages she must pay but instead the court was confronted by the absurd irony of a UKIP MEP claiming EU sovereignty and immunity as an MEP from action in the British courts.
“This may be justice delayed but it will not be justice denied. We are totally determined to hold her to account for the defamatory allegations she made against us.”
Their complaint followed the speech in which Ms Collins referred to the role of local MPs in the child abuse scandal in Rotherham revealed by the Jay report in August 2014.
A judge decided in April last year that the words she used meant, as an allegation of fact, that each of the MPs knew many of the details of the exploitation yet deliberately chose not to intervene but allowed it to continue.
They also meant, as expressions of opinion, that they acted in this way for motives of political correctness, political cowardice or political selfishness and that they were guilty of misconduct so grave that it was or should be criminal, as it aided the perpetrators and made the MPs just as culpable.
Lawyers for Mrs Collins argued that it was a political speech which did not contain any allegation of fact, but expressed an opinion to the effect that the MPs were likely to have known that sexual exploitation was a serious problem in the area.
The amount of compensation could not be agreed so the case came back to court this week for the assessment of damages.
However, Mrs Collins asked the court applied to set the agreement aside, claiming she did not give informed consent and there was no proper acceptance.
She said she was under the impression that her lawyers were going to robustly contest the claim and there were defences available.
Ms Collins also raised the question of whether her role as an MEP gives her immunity.
Mr Justice Warby said he was obliged to grant a “stay” on the proceedings at London’s High Court pending the opinion of the European Parliament.
The judge was informed by officials in Europe that the matter would be dealt with as expeditiously as possible.
Gavin Millar, QC for the MPs, said: “It is simply an attempt to get out of the bargain she made and yet another example of her inability to accept the consequences of her own actions.”
He told the judge: “They have a right to finality and the conclusion of their proceedings in a reasonable time.”
The judge, who reserved his ruling on the application until matters in Europe are resolved, ordered Ms Collins to pay £15,000 on account of costs.
The MPs announced in January last year their decision to take action against Mrs Collins over her comments.
A spokeswoman for Mrs Collins said: ““EU law has been supreme to UK law since the Factortame case of 1988 and this is something the Labour Party, by supporting the remain campaign, wish to continue.
“It seems bizarre they are so keen for UK law to be supreme when it suits them but not when it suits the country.
“I’d be delighted to hear that they have changed their mind and will now be supporting Brexit rather than have laws made in Brussels and the Luxembourg court.
“Could they please clarify their position because as I understood it they were all for the UK being trapped in political union.”