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Debate about MPs' second jobs dominated Prime Minister's Questions, after an undercover investigation involving Jack Straw, Sir Malcolm Rifkind and a bogus Chinese company.

Ed Miliband wants a ban on paid directorships and consultancies, while David Cameron said having people with outside interests made for a "stronger Parliament".

MPs are debating the subject in the House of Commons, where the Liberal Democrats are likely to join the Conservatives in opposing Labour.

The numbers

More than 100 MPs declare additional employment in the Register of Members' Interests, without including things such as occasional TV appearances, book royalties and giving speeches. Of the 108 MPs counted using this methodology, 17 are Labour and 80 are Conservatives, according to BBC Analysis and Research.

Top earners

Comparing MPs' outside earnings is complicated as they often relate to different timescales. One recent analysis, prepared by statistics company Statista and published in the Independent, puts former Prime Minister Gordon Brown at the top, followed by Conservative Geoffrey Cox and Respect MP George Galloway.

Based on the most recent Register of Members' Interests, Mr Brown recorded payments totalling £533,024.50 between 14 October 2014 and 5 December 2014. This did not include money received for flights, accommodation, or paying his staff. He has said all the money goes directly to charity or to help fund charity work.

Another high earner is Mr Cox, a barrister, who registered payments in October 2014 totalling £452,545 for work dating back to September 2013.

Mr Galloway registered media work between April 2013 and November 2014 with payments totalling £303,350 (see below).

Many MPs hold directorships, of the type Labour is trying to ban. But there are plenty of other occupations, which would not be affected by its plans.

Lawyers

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A number of MPs work as solicitors or barristers alongside their day jobs. Conservative MP Sir Edward Garnier, who earned £275,584 last year working as a QC, said being an experienced barrister made him a better MP and that his constituents were able to vote him out if they objected to it. "There will always be barristers who will bring their knowledge to the House of Commons, and if Parliament doesn't want them, Parliament won't have them," he added.

A GP

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Phillip Lee remains a practising GP alongside his work as the Conservative MP for Bracknell, Berkshire. In a Commons debate in 2013, he said the weekly work made him a better MP. He has previously called for MPs' pay to be increased, saying he took a £50,000 pay cut when he joined Parliament.

Farmers

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Conservative MPs Glyn Davies and Robert Goodwill are listed as farmers. Mr Goodwill is also the managing director of a company offering environmentally friendly burials in the North Yorkshire countryside.

A dentist

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Sir Paul Beresford, Conservative MP for Mole Valley works as a dental surgeon for Beresford Dental Practice. In December, he told Get Surrey: "When I became the MP for Mole Valley, they wanted people who had more strings to their bow, rather than people who knew nothing about life.

"If I had gone for selection without another job, then I would not have been successful."

A lecturer

Image copyright PA Image caption Labour's Tristram Hunt works as a history lecturer

David Cameron was quick to point out the shadow education secretary, Tristram Hunt, during Prime Minister's Questions. The Labour MP for Stoke-on-Trent Central declares a salary as a lecturer in modern British history at Queen Mary, University of London.

The media

Image caption MP Diane Abbott and former MP Michael Portillo are regulars on This Week, presented by Andrew Neil

Conservative MP Nadine Dorries' appearance on ITV1's I'm a Celebrity... Get Me Out of Here in 2012 was a one-off but a handful of other MPs earn a regular income from TV work.

Labour's Diane Abbott is a regular pundit on BBC politics show This Week. She recorded 17 payments of £700 each relating to the programme between December 2013 and November 2014 on the register of member's interests.

Respect MP George Galloway, meanwhile, is paid for a weekly news show on Iranian news network Press TV. Between May 2013 and October 2014, the Bradford West MP declared 18 monthly payments of £6,600 each for one hour's work a week. He also presents two programmes per month for Al-Mayadeen TV, for which he is paid £6,000 each month plus return flights to Beirut.

Last year Mr Galloway's spokesman told Press Gazette: "He does believe in spreading his message as widely as he can - not just through the prism of Parliament."

Directorships and consultancies

Many of the MPs with second jobs hold these types of role, which Labour would like to ban.

Speaking in PMQs, Mr Miliband said his plan to ban MPs from being paid by businesses to work as directors or consultants while serving at Westminster would be a "big test" for the government.

But Mr Cameron has said Parliament is "enriched" by MPs with second jobs, and does not favour a complete ban, describing this as a "fundamental disagreement" with Mr Miliband.

Union debate

Image copyright PA Image caption MPs' second jobs dominated Prime Minister's Questions

During Prime Minister's Questions, Mr Cameron said Labour's proposal would still allow an MP to be a "paid trade union official".

The Labour leader offered to add this definition to paid consultant and director in the Labour motion if he would agree. BBC political editor Nick Robinson said he was unaware of any Labour MPs who are paid to be union officials, although many MPs receive union funding for their private offices.

Full-time job?

Not all politicians agree on whether all of an MP's time should be taken up by work at Westminster and in their constituency. Speaking on Monday night, Labour MP John Mann told BBC Radio 4's The World Tonight programme he did not see how there could be time for other employment.

"My day began at 06:00, without a break I worked through to 22:00," he said.

"That is a standard Monday. In reality, when Parliament is sitting, most MPs have two jobs - a full-time job in their constituency and a full-time job at Westminster."

Image copyright PA Image caption Lord Heseltine says MPs should be allowed other jobs alongside their Parliamentary work.

But in an interview on BBC Newsnight, former Deputy Prime Minister Lord Heseltine said he believed an MP's salary was "not designed to be the total income of all MPs".

He said: "Is an MP expected to be a full-time employee of his or her constituency?

"My own view is that it is not a full-time job, there's a huge commitment in it and you work all hours and all days but there is plenty of time in which you can do do other things providing it's within the rules that are laid down."

Public opinion

According to a recent YouGov poll, people are "overwhelmingly against" MPs having any second jobs. Only 26% agreed with the statement that "some MPs continuing to do second jobs like medicine, law or running a business keeps them in touch with ordinary people, and is better than having a House of Commons made up of just full-time politicians".