Special filters are to be installed at Leicester's crematorium to stop poisonous gases from metal fillings and pacemakers entering the atmosphere.

Leicester City Council is to spend more than £300,000 to cut the amount of mercury released when people are cremated at Gilroes cemetery.

The new machinery will be installed within three years and will include technology to filter out poisonous gases.

Mercury pollution has been linked with birth defects, kidney disease and multiple sclerosis, with cremations causing almost a sixth of all UK emissions of the metal.

Without new safeguards, crematoria would become the biggest single cause of mercury pollution in the country by 2020.

In an attempt to prevent more mercury getting into soil, water and food, the Government has ordered half of crematoria nationally to fit the new equipment by 2012.

Leicester is the seventh biggest council in the country in terms of burials and cremations, so is on the list.

How and when the changes will be made will be included in a nine-month review of the council's bereavement services.

That started this month, led by city councillor Paul Newcombe.

He said: "We will have to extend our existing crematorium to make room for this larger equipment.

"It is not going to be cheap, but there has been no discussion as yet on whether this will lead to an increase in the cost of cremations.

"There has been no formal review of the service since 2003. Our review will be wide-ranging.

"We will look at the services we offer, the condition and quality of our facilities and whether there are new sites needed and where these might be."

A panel of councillors will also consider how to manage the growing number of burials.

Coun Newcombe said: "To make this a valuable review, we will be looking at where councils re-use graves, but I think that this should always be the absolute last resort.

"We must explore all other options before we consider something like that."

Leicester City Council runs four cemeteries, Gilroes, Saffron Hill Cemetery, near Saffron Lane, Welford Road Cemetery near the University of Leicester, and another in Belgrave.

Welford Road and Belgrave are full or nearly full, while Gilroes and Saffron Hill will be full within 40 years.