A Fianna Fáil frontbencher says his party "isn't progressing enough" amid growing speculation over Micheal Martin's leadership.

Niall Collins comments come after Fianna Fáil failed to win a seat in either of the weekend's Dáil by-elections - with the results expected to be raised as a "matter of concern" at the next parliamentary party meeting.

Several TDs are reported to have expressed anger at the party leadership for not capitalising on public anger at the water charges.

However, Justice Spokesperson Niall Collins says Micheál Martin isn't to blame.

Last week, Fianna Fáil TD Eamon O’Cuiv told Newstalk Breakfast his party's strategy is wrong.

The criticism of the party comes after a poll showing support for Fianna Fáil has dropped 5 points to 20%.