US Attorney Preet Bharara was fired by Donald Trump to stop him from investigating his financial affairs, senior Democrats have suggested.

His sacking came days after ethics campaigners asked him to investigate "payments and financial benefits from foreign governments" benefiting the new President, which could have potentially breached his constitutional duties.

Mr Bharara, who oversaw the powerful and affluent southern district of New York, was one of 46 chief federal law enforcement officers fired or asked to resign by Mr Trump last week.

Taking to Twitter, he made it clear that he "did not resign" and had been fired from the role.

Senior Democrats have now suggested that the President was worried about a potential investigation by Mr Bharara who made national headlines after investigating Sheldon Silver, the long time speaker of the New York State Assembly for taking millions of dollars in payoffs. Mr Silver was subsequently convicted on all counts.

A separate investigation secured the conviction of a number of politicians and officials over a complex scheme involving bribery to secure a place on the Republican ballot in the 2013 New York City mayoral election.

Representative Elijah Cumming suggested that this had prompted Mr Trump to order Mr Bharara's firing.

"There's a lot of questions coming up as to whether President Trump is concerned about the jurisdiction of this US attorney and whether that might affect his future," he told ABC News.

Last week Mr Bharara was asked to look into foreign payments received by Mr Trump in an open letter signed by campaign groups such as Citizens for Responsibility and Ethics in Washington.

They said they feared that the US may be "exposed to foreign governments directly and indirectly providing payments and financial benefits to President Trump when those foreign governments may be seeking to influence Executive Branch policies and positions."

Mr Cummings' concerns were echoed by Senator Elizabeth Warren, who tweeted: "You can't fire the rule of law, @realDonaldTrump. You can't shut down ongoing investigations by career prosecutors... The Senate confirms US Attorneys. And you're not replacing real prosecutors with cronies w/out a massive fight."

Mr Bharara has been described as one of "the nation's most aggressive and outspoken prosecutors of public corruption," fêted on the cover of Time magazine under the legend "This man is busting Wall St.", and praised for securing the longest-ever sentence for insider trading while shutting down multi-billion dollar hedge funds.

It was reported in November that Mr Bharara had met with Mr Trump for a discussion brokered by Senator Charles Schumer.

After the Trump Tower sit-down, he told reporters: "I agreed to stay on."

Before his sudden dismissal this weekend, the Indian-born lawyer refused to step down and ignored an unorthodox personal phone call from Mr Trump's office.

It is not unusual for presidents to appoint loyalists to many of the 93 US Attorney positions across the nation.