ALL MPs should be made to pay any profit made from their second homes back to the taxpayer, the Liberal Democrats said yesterday.

Party activists voted to adopt the sanction – already voluntarily accepted by Lib Dem front-benchers – at the party’s annual conference in Bournemouth.

Any MPs found to have broken the rules should be subject to criminal investigations, the party said.

Anger at the expenses scandal boiled over during the debate, with one MEP saying he was furious at the “dirty cheating b********” who had used taxpayers’ money to line their pockets.

Party leader Nick Clegg has argued that the Liberal Democrats have been less damaged from the scandal than other parties.

Some MPs were found to have “flipped” the designation of their Westminster and constituency properties to avoid paying capital gains tax, but no Lib Dem had done this, Mr Clegg said.

The Lib Dems are to outline plans for a tax on owners of £1m-plus homes, using the proceeds to help low-paid workers.

Treasury spokesman Vince Cable will announce plans for a 0.5% annual levy on the most expensive homes, raising £1bn, at the party conference later.

He will say it would help fund plans to get four million people earning less than £10,000 out of tax altogether.

He will warn of "unpopular" choices on tax and spending but attack the Tories for being "cynical and dishonest".

The new charge would mean additional tax of £2,500 a year on a home valued at £1.5m, or £15,000 a year on a property worth £4m.

Party leader Nick Clegg told the Independent: "That is not a big sacrifice. It is a perfectly reasonable thing to ask of people who have got properties of that value, and it's completely in line with how pretty well every tax system in the world works.

"I think people who live in properties worth over £1m feel it's fair; in this day and age, to pay about £2,000 or less to help people for whom the tax burden is much higher."

Lib Dem leaders have turned their fire on the Tories at their annual gathering in Bournemouth, arguing they cannot be trusted to tell the truth on spending and are posturing about planned cuts without being prepared to give details.

Mineral-rich African states have been deprived of huge sums of royalties and taxes by mining firms, a report says.

The report, by prominent development charities, blames a lack of legislative oversight and excessively generous tax concessions agreed with the firms.

It says some mining companies have also avoided paying tax through secret contracts with African governments.

The study covers South Africa, Sierra Leone, Ghana, the Democratic Republic of Congo, Malawi, Tanzania and Zambia.

Commissioned by development charities including Christian Aid and ActionAid, the Breaking the Curse report calls for reform of the institutional framework that negotiates mining concessions and monitors the royalties paid.

Even in the boom times, African nations failed to profit as much as they should have done from natural resources thanks to inadequate tax rules and lack of ability to enforce the rules that did apply, the report says.

Ghana, a top African gold producer, is losing $68m (£46.7m) annually because it is receiving low royalties, the report's authors estimate.

They believe Tanzania, the continent's third largest producer of gold, could be losing $30m (£20.6m) a year in potential revenues.

And low royalty rates could be costing South Africa, the continent's biggest gold producer, up to $359m (£246m) a year, the report says.

However, in South Africa, where the government has decided to defer royalty payments this year to help secure jobs in the mining sector, finance minister Trevor Manuel questioned the researchers' figures.

Mr Manuel said his country would lose $195m (£133.9m) in deferred royalties this year.

The report says African countries have been encouraged by agencies such as the World Bank to offer more generous terms to attract mining investment.

Essentially, the BBC's business reporter Mark Gregory says, it argues the costs of this approach have outweighed the benefits.