Former Trump personal attorney Cohen testifies before House Oversight hearing on Capitol Hill in Washington.

Washington - President Donald Trump's former lawyer Michael Cohen testified to Congress on Wednesday that reimbursement checks issued to him for hush-money payments to an adult film star were signed by Donald Trump Jr. and the Trump Organization chief financial officer.

Cohen said Trump himself signed a $35 000 check repaying him for "hush money I paid on his behalf" while Trump was president, Cohen told a House of Representatives' committee.

"Other checks to reimburse me for the hush money payments were signed by Don Jr. and Allen Weisselberg," he said.

Cohen's testimony raises the possibility that Donald Trump Jr. could be prosecuted for violating campaign finance laws, depending on what he knew about what the payments were intended for, said lawyer Andy Wright, who served as associate counsel to President Barack Obama.

Alan Futerfas, a lawyer for Trump Jr., did not immediately respond to a request for comment. Rudy Giuliani, a lawyer for Trump, declined to immediately comment on Cohen's testimony.

Cohen pleaded guilty in August to campaign finance violations over his arrangement of payments to adult film star Stormy Daniels and to former Playboy model Karen McDougal.

On Wednesday, Cohen said Trump directed him to use his own funds from a home equity line of credit to pay Daniels to avoid any money being traced back to Trump. Cohen said he was going to jail, in part, because of his decision "to help Mr Trump hide that payment from the American people before they voted a few days later."