MP Sally Keeble and Dr Ron Zimmern on the IVF debate

Louise, from Bristol, was born 20 years ago on Saturday after her mother was given in vitro fertility treatment.

Dozens of other IVF babies are to join the party, which will be hosted by public health minister Tessa Jowell and television presenter Cheryl Baker.

Ms Jowell is concerned about the lack of a national framework for IVF treatment.

This leads to different heath authorities setting different criteria for who should get treatment.

No proper organisation

She said: "The situation at the moment is a mess. There is no national framework or proper organisation.

Louise Brown: the world's first test-tube baby

"We expect resources to be spent in the most effective way and in a way that is geographically equitable. What is not acceptable is neighbouring authorities having radically different priorities."

The government has asked the Royal College of Obstetricians and Gynaecologists to draw up guidelines on infertility treatment for GPs, hospital doctors and IVF specialists in an effort to stamp out the inequalities.

Ms Jowell said: "We want to ensure that people undertaking enormously costly cycles of treatment do so on the basis of rigorous and expert assessments of the likelihood of becoming pregnant."

Inconsistent

She will be joined at the House of Commons party by Northamptom North MP Sally Keeble, who herself had IIVF treatment.

She is a keen advocate of national guidelines on IVF treatment.

She was denied NHS treatment on the grounds of her age. "The criteria is inconsistent and not generally known," she said.

But not everyone is in agreement. Dr Ron Zimmern from Cambridge and Huntingdon says that, if health authorities are obliged to set aside some money for IVF treatment, there will be less for other priority areas, such as cancer treatment.

"If we are obliged to put money into IVF, it cannot be used for other services which we believe are of greater priority," he said.

"If resources are finite, for every good news story comes a bad news story which is hidden and the bad news story is our inability to use that money to fund other services."

Pioneering

Since Louise's birth in 1978, another 29,000 British babies have been born by IVF. One of them is Louise's sister, Natalie.

Around 200,000 have been born around the world.

The IVF technique was pioneered by Patrick Steptoe and Professor Robert Edwards at Bourn Hall Clinic near Cambridge. Professor Edwards is expected to attend Louise Brown's birthday party.

It involves fertilising the egg in a laboratory and implanting it back in the mother's womb.

The success of IVF treatment varies according to a number of factors, including the age of the mother.