Washington - Hillary Clinton's presidential campaign and the Democratic National Committee helped fund political research into President Donald Trump that ultimately produced a dossier of allegations about his ties to Russia, a person familiar with the matter said on Tuesday night.The revelation is likely to fuel complaints by Trump that the dossier, which the president has derided as "phony stuff", is a politically motivated collection of salacious claims. Yet the FBI has worked to corroborate the document, and in a sign of its ongoing relevance to investigators, special counsel Robert Mueller's team - which is probing potential co-ordination between Russia and the Trump campaign - weeks ago questioned the former British spy, Christopher Steele, who helped compile the claims in the dossier.The dossier, which circulated in Washington last year and was turned over to the FBI for its review, contends that Russia was engaged in a longstanding effort to aid Trump and had amassed compromising information about him. Trump has repeatedly dismissed the document as false and in recent days has questioned on Twitter whether Democrats or the FBI had helped fund it.Trump has also attacked the findings of the FBI, NSA and CIA that Russia waged a large-scale influence campaign to interfere in the election. The FBI and the CIA have said with high confidence that the effort was aimed at hurting Clinton's candidacy and helping Trump. The NSA found the same with "moderate" confidence."But let's be clear, there is a serious federal investigation into the Trump campaign's ties to Russia, and the American public deserves to know what happened," the DNC said in a statement. The dossier created a political firestorm in January when it was revealed that then-FBI Director James Comey had alerted Trump to the existence of allegations about him and Russia.