The Unmarried Fathers of Ireland group have told the Sunday Tribune that they are considering blocking the motorway in protest at the jailing of "an innocent man" for failing to keep up child maintenance payments to his former wife.

The man, who lives in Carlow, was sentenced to three months in Mountjoy jail for breaching a court order which obliged him to pay 1,800 a month to his ex-wife for three children . . . only one of whom is his biological child. A judge in a family law court in Trim sentenced the man over a week ago as he was not capable of keeping up the weekly payment of 150 per child.

The 40-year-old man, who cannot be named due to the incamera rule which restricts reporting of family-law cases, has been separated from his former wife for two years.

"This man is not a criminal, he is an innocent man and should not have been locked up, " said Ray Kelly, national director of the Unmarried Fathers of Ireland group. "We believe it is unconstitutional for anyone to be locked up for non-payment of a bill. We are calling on justice minister Michael McDowell to intervene and see that he is released from Mountjoy immediately. He only earns 2,000 a month and he is expected to pay his ex-wife 1,800 of that in maintenance for three children, even though two of them are not biologically his."

The Unmarried Fathers of Ireland group is planning a series of protests this week.

"We are fearful for this man's life in Mountjoy after everything that has happened this week, " said Kelly, "so we will do whatever is necessary to get him out.

"We are considering blocking off the M50 on Monday and maybe if we stop all the bank holiday traffic, people will start to take notice of the way unmarried fathers are treated in this country."