Washington, Jul 6 (IANS): The US' Environmental Protection Agency (EPA) chief Scott Pruitt has resigned after months of ethics controversies, citing "the unrelenting attacks" on himself and his family, which "have taken a sizable toll on all of us".

President Donald Trump first tweeted the news on Thursday that Pruitt had resigned, reports CNN.

"I have accepted the resignation of Scott Pruitt as the Administrator of the Environmental Protection Agency," Trump tweeted.

"Within the Agency, Scott has done an outstanding job, and I will always be thankful to him for this."

Trump also said that Senate-confirmed deputy Andrew Wheeler will assume the duties of acting administrator of the EPA from July 9.

"I have no doubt that Andy will continue on with our great and lasting EPA agenda. We have made tremendous progress and the future of the EPA is very bright!" Trump tweeted.

Pruitt's resignation follows months during which the EPA administrator has been embroiled in one ethics controversy after the next.

It also comes two days after an exclusive CNN investigation revealed a former top aide alleged Pruitt and his staffers held regular meetings to "scrub", alter or remove controversial events from his calendar.

The investigation sparked two Democratic congressman to call on Thursday for the EPA inspector general to investigate whether Pruitt committed a federal crime.

Pruitt's resignation letter to Trump offered regret about leaving the role, but said "unrelenting attacks" had taken a toll.

"It is extremely difficult for me to cease serving you in this role first because I count it a blessing to be serving you in any capacity, but also, because of the transformative work that is occurring," Pruitt wrote.

"However, the unrelenting attacks on me personally, my family, are unprecedented and have taken a sizable toll on all of us."

Pruitt, an Oklahoma Republican, came to the job as one of the EPA's chief critics and was seen as someone philosophically at odds with the agency Trump tapped him to run.

While serving as Oklahoma's attorney general, Pruitt was one of the chief architects of the legal battle against Obama's climate change policies and repeatedly sued the agency.