David Cameron has been accused of using the Queen to drum-up support for his campaign to keep the UK in the EU after the monarch warned "division in Europe is dangerous".
Ukip leader Nigel Farage claimed the monarch had been "very poorly advised" after she made the speech at a state banquet in Germany, where Chancellor Angela Merkel and Cameron were present.
"It's been a rotten week for the monarchy after the row with the SNP too. She must not let the government pressure her into saying things that appear to influence the referendum," Farage said.
"She is, after all, the head of the Commonwealth as well as head of the UK, and there is a potential conflict of interests there."
But Buckingham Palace has maintained that the Queen, in line with her constitutional duty, is above politics and the speech was politically neutral.
At the time, the monarch said: "We have witnessed how quickly things can change for the better. But we know that we must work hard to maintain the benefits of the post-war world.
"We know that division in Europe is dangerous and that we must guard against it in the west as well as in the east of our continent. That remains a common endeavour."
Farage made the accusations ahead of Cameron's meeting with EU leaders at a two-day European Council summit.
Cameron, speaking after the meeting, said he was "delighted" that the renegotiation discussions had started.
The PM said: "I am delighted that the process of British reform and renegotiation, and the referendum we are going to hold – that process is now properly under way.
"People always say to me 'these things aren't possible, we will never get them done'. Once again, we have proved we will get them done."