Two mothers jailed for drug-related offences have lost their High Court battle for the right to keep their babies with them in prison beyond the age of 18 months.

The court also warned that the increasing number of pregnant women and mothers of young children involved in the drugs trade cannot expect lenient treatment.

Two judges rejected claims that forcing the women in the test case to part from their children would be "a clear interference" with their human rights.

Both women, known only as P and Q, were refused permission to appeal but their lawyers indicated that they will now ask the Court of Appeal itself to hear their cases.

Lord Woolf said the applications should be made as a matter of urgency because "the longer the babies remain with their mothers the more difficult it is to separate them". He called for the applications to be made by next week.

Prisoner P was seeking judicial review of a decision that her baby daughter, born in July 1999, should no longer be allowed to remain with her at the mother and baby unit in Styal prison, Cheshire.

The 32-year-old Jamaican woman is serving an eight-year sentence for smuggling cocaine. She came to England in March 1999, when five months pregnant, and was arrested at Gatwick airport.

If her appeal bid fails, her daughter is likely to be placed with foster carers. Moves to take away the child in January were postponed pending the outcome of this case.

In the second case, Prisoner Q brought a similar challenge against the Prison Service. Q, from Brixton, south London, is serving a five-year sentence at Askham Grange, York, after being convicted in March last year of conspiracy to supply cannabis.

Her daughter was born in July 1999 while she was on bail and will be three when she first becomes eligible for parole in July 2002.

Lawyers from human rights specialists firm Hickman Rose said: "P will pursue an appeal against this very disturbing judgment.

"The court has failed to address the legal vacuum that P and her child are in, as a result of a rigid Prison Service policy to separate mother and child at 18 months."

The firm said the provisions to make the rights of the child paramount within the 1989 Children Act had been "side-stepped" by the judgement.

Solicitors acting for Q said they were "extremely disappointed" with the ruling and claimed it was aimed at "narrowing any scope for use of the Human Rights Act". They also plan to appeal.

In his ruling Lord Woolf said the policy of separating babies from their mothers at 18 months raised issues "of an extremely sensitive nature".

He added: "No one would suggest that it is desirable, if this can be avoided, for a mother to give birth to or have a child with her in prison."

But he said was becoming more common as more women were becoming involved in the drugs trade and he warned that if courts were lenient on expectant mothers involved in drug smuggling, it would send a message to drug barons to make even greater use of pregnant women and mothers with young children than they do already.

Lord Woolf ruled said the provisions of the Children Act did not apply in the context of the Prison Service because people were sent to jail as a punishment, a consequence of which was inevitably the impairment of the right to family life.

He also hinted that there was evidence to suggest that children should be removed from their mothers in prison earlier when the bond was not so strong.

In Germany and Spain, mothers are allowed to have their children with them in prison until the age of six, in the Netherlands until four in one prison, and until three in Portugal and Switzerland. One German jail has an open unit outside the prison walls in which each mother has her own apartment.