A union representing public servants has reached a tentative contract that it says gives federal scientists the right to share their research with the media without first being designated official spokespeople.

The Professional Institute of the Public Service of Canada (PIPSC) says it has reached tentative agreements involving more than 18,000 public servants.

The union attached a priority to a provision that allows scientists to speak about their research after allegations that the former Conservative government "muzzled" scientists amid vast funding cuts.

The PIPSC represents some 55,000 scientists, information technology experts, auditors and other public service professionals, most of whom work for the federal government.

The union says its last contract expired in 2014.

The contract also includes a five per cent wage increase over four years. The agreement is retroactive to 2014.

Negotiations are ongoing for more than 32,000 other PIPSC members.

Treasury Board President Scott Brison says the government has approached the negotiations with the goal of restoring "a culture of respect for Canada's public service."

"We remain committed to reaching agreements with the rest of the public service through fair and respectful negotiations," Brison said in an emailed statement.