Q&A: Brown's immunisation bond plan

Gordon Brown has pledged the UK to give $1.4bn towards the scheme

Chancellor Gordon Brown is launching a new programme to fund child immunisations in the world's poorest countries.

The $4bn (£2.1bn) International Finance Facility for Immunisation (IFFIM) is intended to pay for 500 million children to be immunised over the next 10 years.

Diseases covered include polio, measles, diphtheria and hepatitis.

How much money is the UK putting forward and how will it be raised?

The UK has pledged to donate approximately $1.4bn over the next 10 years.

It is raising the money though the issuing of a new government bond, on which the Treasury will pay interest of roughly 5%. It will also pledge to buy the bonds back.

The bonds are being issued on the international markets, and other nations already signed up to IFFIM - France, Italy, Spain, Sweden and Norway - are about to do the same.

South Africa and Brazil are also proposing to follow suit.

It all sounds good, but why has the bond scheme met with some opposition?

Basically because it appears unnecessarily obtuse.

The scheme aims to immunise 500 million children

The BBC's economics editor, Evan Davis, has described IFFIM as "a rather complicated bit of financial engineering".

Critics of IFFIM point to the fact that it would have been much easier - and cheaper - for the government simply to add extra funds to its existing overseas aid budget.

They also say that by issuing the new bonds, the government is able to keep the $1.4bn "off the books", as it will not show up in the UK's national debt figures.

The critics add that, most importantly, IFFIM is also reducing future aid payments, as the government intends to pay the interest on the new bonds from future aid budgets.

What is the government's defence?

Gordon Brown counters that the issuing of a new bond is vital, as it is the best way of getting the money available immediately.

"The reason we have done it this way is we want to spend the money now, we want the vaccinations to take place because lives can be saved now," he told the BBC's Today programme.

"I don't think it is anything to do with saving money or what happens to the national debt. It is to do with getting action as quickly as possible, so young lives can be saved by the vaccinations happening very quickly."

Why is the US not involved yet?

Some critics have said it is impossible for the US to get involved in IFFIM because the new bonds have to be paid for from future budgets, which is illegal under federal law.

Gordon Brown insists this is not the case - and that the rest of the world simply has to wait for the political will in America to swing behind the scheme.

This could depend upon the results of the forthcoming mid-term elections.