Mr Hague said Mr Miliband's comments were 'contemptible'
Shadow foreign secretary William Hague has launched a fierce attack on David Miliband for "disgraceful remarks" he made in his Labour conference speech.
Mr Miliband accused the Conservatives of having links with far-right politics in Europe, including a Latvian party that he said celebrated the Waffen SS.
Now Mr Hague has written to the foreign secretary to demand an apology.
He warned the remarks "could damage relations with Latvia" and other countries who suffered under communism.
Speaking to delegates on Thursday, Mr Miliband criticised the Tories' new allies in the European Conservatives and Reformists Group, calling them "a collection of outcasts".
Repeating Labour's claims that they included a Latvian party which celebrates the "Latvian Waffen SS with a march past of SS veterans", he also attacked Tory chairman Eric Pickles who, he said, had told the BBC they should not be condemned because "they were only following orders".
"It makes me sick," said Mr Miliband.
The row has now escalated with Mr Hague's letter in which he said he was "appalled" at the comments and claimed they were factually inaccurate.
"Your remarks are a slur on the reputation of a country that is a good friend to Britain and a close ally in Nato and the EU," he wrote.
"There is a real danger that you could damage relations with Latvia and other countries who suffered under totalitarian communist rule."
Mr Hague also demanded an apology for "contemptible" comments about Mr Pickles and also remarks about Polish MEP Michal Kaminski, whom Mr Miliband accused of having an "anti-Semitic, neo-Nazi past".
The letter goes further by launching a counter-attack on Labour for allegedly having links to controversial European politicians.
Mr Hague said Labour MEPs "sat alongside an MEP from the Polish Self-Defence Party, whose leader has praised Adolf Hitler", and an Italian MEP "who has promoted the conspiracy that the CIA was responsible for 9/11".
He added: "Democratic politics is at its best when it is a civilised and constructive debate between different points of view. It is deeply regrettable that you have listened to those who prefer the politics of slur and smear."