Union members want regional titles to be protected by the UK government
A union representing journalists working for owners of the Western Mail and Daily Post says it is concerned for the future of the newspapers.
The comment came in evidence presented to the assembly broadcasting committee.
A National Union of Journalists (NUJ) representative has described it is a "crisis".
Media Wales, which controls the Western Mail and Echo, told AMs competition laws needed to be changed or newspapers could be at risk of closing.
Alan Edmunds, editorial director of Media Wales, which controls the Western Mail, South Wales Echo and weekly titles in south Wales, said it was putting in more investment in technology and training for journalists, with extra investment and more news online.
But he told the committee that competition laws needed to be reviewed in the light of the changing economic environment.
"If the Government doesn't act soon then we could see more vulnerable titles disappear from our market places," he said.
Martin Shipton, who is the head of the NUJ branch for Media Wales in Cardiff, said the current state of the newspaper industry in Wales now warranted raising the matter with the assembly government.
He told the committee that investors and shareholders had to get used to lower returns or the Western Mail's future will be threatened.
"Our concern is that if those very high rates of return are still sought... the Western Mail and its associated newspapers may no longer exist," he said.
Mr Shipton said earlier that the crisis was a threat to jobs in Wales and undermined an essential element of Welsh democracy.
He said the results of the changes weren't yet clear but he was not happy with the developments.
"Decisions that have been taken have not been in the best interests of news in Wales," added Mr Shipton.
In his evidence to the committee, Mr Shipton is calling for a media forum to monitor structural change in the Welsh media.
He also wants the assembly ministers to press the UK government for a commitment to protect newspaper titles, if it relaxes current regulations on cross-media ownership.
Media Wales owners Trinity Mirror announced last week a merger of its business operations in Wales and in northern England.
But the company said that despite a shake-up of senior management there were no plans to merge paper titles or move printing of the Western Mail outside Wales.
However, it did confirm that two senior managers, managing director Keith Dye and finance director Stuart Thomas, had left Media Wales with immediate effect.
A spokesperson for the Trinity Mirror group said it would be responding to the comments after Thursday's assembly meeting.