Foreign Secretary William Hague will address the House of Commons today on the "terrible situation in Gaza".

In recent days, Hague has blamed the latest round of violence on Hamas which "bears principal responsibility" - though he has also stated that Israel has a duty to "de-escalate the violence, to avoid civilian casualties, to observe international humanitarian law".

Yesterday, on behalf of Conservative Friends of Israel, 17 Tory MPs wrote to the Daily Telegraph urging the Government to maintain its stance of not dealing with Hamas, which they blamed for escalating the violence in the region.

Separately, eight other Tory MPs have signed a petition supporting UN recognition of an independent Palestinian state. Fifty-six Labour MPs and 16 Lib Dem MPs have also signed the same pro-Palestine petition.

In fact, the State of Israel and the Palestinians are both well-represented by parliamentary groups in the halls of Westminster, which often sponsor MPs to take trips to the region. Hague himself, for example, has been a member of the Conservative Friends of Israel since he was 15.

But what do we actually know about these groups and their supporters in the Commons?

Conservative Friends of Israel (CFI)

CFI was set up in 1974. The current chair is MP James Arbuthnot. As its website puts it: "With close to 2,000 activists as members – alongside 80% of Tory MPs – CFI is active at every level of the Party."

When asked about which specific Tory MPs and peers were members of CFI, a spokeswoman told the Huffington Post UK: “Its much more grey than that. We don’t have a list of members its just based on who comes on trips speaks and speaks on issues."

A Dispatches documentary in 2009, presented by Tory-supporting journalist Peter Oborne, claimed that at least half of the then-shadow cabinet were affiliated members of CFI.

As Prime Minister, David Cameron told the CFI: “My belief in Israel is unbreakable and commitment to Israel’s security is non-negotiable."

Conservative Friends of Palestine?

Well....there aren't any Conservative Friends of Palestine. The Tories do not have an equivalent group. The nearest they have is the Conservative Middle East Council which aims to help "parliamentarians to gain a unique, first-hand understanding of the Middle East."

Again, the CMEC does not have official affiliates but, helpfully, "all Conservative MPs are considered members."

A recent CMEC statement, signed by president Nicolas Soames MP, says it is "imperative that another Israeli ground invasion of the Gaza strip must be averted: such an action would surely lead to an even greater civilian death toll, a significant loss of international sympathy and support for Israel, and a prolonged and deepening conflict across the occupied Palestinian territories."

Labour Friends of Israel (LFI)

Founded in 1957 to strengthen the bond between Labour and the Israeli Labor Party, LFI is a supporter of a two-state solution and strong bilateral relations between the British and Israeli governments. Tony Blair, now the Middle East 'peace envoy, was one of its most high-profile members.

A spokesman told the Huffington Post UK: "We have a core group of officers in the House of Commons, which include our Chair: John Woodcock MP, and Vice Chairs: Michael Dugher MP, Louise Ellman MP, Michael McCann MP, Rachel Reeves MP and Jonathan Reynolds MP.

"LFI also has a large number of other supporters in the House of Commons, which include both shadow cabinet members and backbenchers, but we don’t list them as members.

"We also have a large number of supporters in the House of Lords, led by Baroness Ramsay."

In the 2009 Dispatches documentary, LFI was accused of being "less unquestioning in its support of the Israeli government than CFI". It is also believed to have paid for more MPs to take free trips to Israel than any other group – more than 60 between 2001 and 2009.

Labour Friends of Palestine (LFP)

LFP was only set up in 2009, during Israel's previous bombardment of Gaza ("Operation Cast Lead"). At the 2012 Labour Party annual conference in Manchester, Ed Miliband was a guest of honour at the LFP's gala dinner.

The current chair of LFP is Rochdale MP Simon Danczuk. More than 80 Labour MPs' names are listed on the group's site as "supporters" of the group - curiously, Miliband and shadow foreign secretary Douglas Alexander don't appear on the list.

A spokesman for the group told the HuffPost UK: "We are trying to raise awareness within the Labour movement - parliamentarians, members, trade unionists - about the reality of the situation in the Palestinian territories. We want to see action taken to implement the two-state solution... and that means blocking settlements and even looking at banning settlement goods from coming into EU markets."

Liberal Democrat Friends of Israel (LDFI)

The LDFI's president is veteran Lib Dem MP Sir Alan Beith. At the time of writing, however, no-one at the LDFI was available to talk about membership numbers.

Liberal Democrat Friends of Palestine (LDFP)

No figures on membership numbers were available at the time of writing but the LDFP grouping has been no stranger to controversy. Lib Dem peer and LDFP member Jenny Tonge was summoned for talks with her leader in 2006 after claiming that the Lib-Dems were "probably in the grip of the pro-Israel lobby."

Six years later, Tonge hit the headlines again after she was accused of calling for the dismantling of the State of Israel. LDFP defended her - but Tonge was forced to resign from the party.