As Congress comes under pressure to pass gun control measures after the elementary school massacre in Uvalde, Texas, Republican Senator Mitt Romney is catching flack for accepting vast donations from the gun lobby.

The Utah lawmaker tweeted his regrets about the massacre as the horror of the event became clear, writing: “Grief overwhelms the soul. Children slaughtered. Lives extinguished. Parents’ hearts wrenched. Incomprehensible. I offer prayer and condolence but know that it is grossly inadequate. We must find answers.”

Many of his detractors immediately responded by pointing to the millions of dollars he has accepted from the National Rifle Association (NRA) – a total that according to the anti-gun campaign group Brady tops out at $13,647,676, more than the NRA has donated to any other Republican senator.

The bulk of Mr Romney’s Senate caucus is expected to oppose any gun control legislation put forward by Democrats in the wake of the tragedy, as it has after other major mass shootings in recent years.

However, Mr Romney himself has signalled he may be open to at least some form of action to stop potentially dangerous people obtaining firearms. Speaking to The Independent, he said he has spoken with two colleagues, Republican Pat Toomey and Democrat Joe Manchin, about their proposed legislation on background checks.

“I’ve long felt that the federal government has responsibility for an effective background check system and if there are ways to improve that, I could be supportive,” he said – adding that he had yet to make up his mind.

The NRA itself, meanwhile, is planning to go ahead with its meeting in Houston, Texas on Friday despite the mass shooting in Uvalde, which killed 19 elementary school students and two adults.

The meeting is set to be addressed by leading right-wing figures including Donald Trump and top GOP figures from Texas, among them Governor Greg Abbott and Mr Romney’s Senate colleague Ted Cruz.

Attendees are prohibited from bringing firearms into the hall where Mr Trump will speak.