Deputy Premier Paul Robichaud denies allegations that he interfered in the prosecution of his brother on fisheries charges and says he has no plans to resign.

"I won’t resign based on the allegations in an anonymous letter," Robichaud said.

The RCMP are looking into anonymous suggestions that Robichaud, who is also the minister responsible for economic development, pressured staff at the fisheries department not to prosecute his brother under the Aquaculture Act.

"I never interfered in any kind of way in the process, before and after," Robichaud told reporters on Wednesday. "If I interfered, I didn't have a lot of success because he went to court," he added.

The case is still before the courts.

Robichaud said no one from his office had any contact with fisheries department supervisors or enforcement officers about the prosecution either.

The Liberals are calling for Robichaud to resign pending the outcome of the RCMP investigation into the allegations.

They point out Alward demanded the same thing when a senior Liberal appointee — Dana Clendenning — was under investigation in 2009.

In 2009, Clendenning, a close friend of then-premier Shawn Graham, was accused of violating the province's Conflict of Interest Act.

Clendenning, who was then president and chief executive officer of NB Liquor, was accused of a conflict for getting paid as a consultant-lobbyist after being appointed as head of the Crown corporation.

But the complaint against him was not anonymous, it was signed by Fredericton businessman Barry O'Donnell.

Clendenning was cleared in 2010, following a hearing in the Court of Queen's Bench.

"If a cabinet minister will have to resign every time an unsigned letter is sent to the Official Opposition, it's probably possible for an Official Opposition to have the resignation of an entire cabinet within 24 hours, of all the members of the Legislative Assembly resign in less than a week," said Robichaud.

He said as a politician, he's used to public scrutiny. But it's unfair for his brother to be subjected to it and he feels badly for him. "A minor charge wouldn't be news if I wasn't his brother," he said.

Alward stands by Robichaud

Premier David Alward is also rejecting opposition calls that he fire Robichaud because of the police investigation into inference allegations.

Alward says he's standing behind his deputy premier.

"I also can say that I have full confidence in the minister of economic development, full confidence in the work he has done in the past, full confidence in the work he's doing today, and he will continue to do on behalf of the people of New Brunswick,” Alward said.

Alward and Attorney General Marie-Claude Blais fired back at the Liberals in question period on Wednesday.

Alward and Blais say it was wrong for the Liberals to suggest they knew about the RCMP investigation.

The issue started when the Opposition received an anonymous letter saying Robichaud interfered with the prosecution against his brother for alleged aquaculture violations.

The Liberals passed the anonymous allegations against Robichaud on to the RCMP and received a letter on Tuesday from assistant commissioner Wayne Lang, the senior officer in New Brunswick, saying the police would investigate.

RCMP Const. Chantal Farrah said on Tuesday that launching an investigation does not mean there is any evidence of wrongdoing by Robichaud.

There have been no charges against Robichaud and nothing has been proven in court.