The former home secretary David Blunkett is reported to have launched a legal challenge against his former lover, Kimberly Quinn, claiming he is the father of her new son born earlier this month.

The former home secretary David Blunkett is reported to have launched a legal challenge against his former lover, Kimberly Quinn, claiming he is the father of her new son born earlier this month.

Mr Blunkett, whose publicity-charged falling out with Mrs Quinn ended with his resignation from the Cabinet, is also claiming that she should not have named the child or registered her husband, Stephen, as the father while the dispute is continuing.

The MP for Sheffield Brightside is understood to have demanded a DNA test on the child, named Lorcan Patrick Quinn, who was born on 2 February.

A similar test established that he is the father of Mrs Quinn's other son, William, two, and he is fighting for access to him. A flurry of letters is said to have been sent by Mr Blunkett's solicitors, the leading human rights firm Bindman & Partners, to Mrs Quinn's legal team at the equally high-profile Mishcon de Reya.

Mr Blunkett's spokesman is reported to have said: "David Blunkett has never discussed or revealed the details of the legal proceedings taking place behind closed doors and has no intention of starting now."

Mr Blunkett was forced to resign after an inquiry found he had "fast-tracked" a visa application for Ms Quinn's nanny, Leoncia Casalme. Allegations that he had acted improperly over Ms Casalme's visa application emerged during his bitter dispute with Mrs Quinn over access to William. His aggressive pursuit of access was widely criticised at the time.

The fact that he appears to be acting equally stridently in his claim to the second child will cast a doubt over whether the Prime Minister will be able to bring him back into the Cabinet soon after the next election.