I've been a member of Labour Friends of Israel for a long time, for a reason unconnected with any religious, ethnic or constituency factors. My mother worked for UNRRA, the wartime organisation which helped the victims of Nazism find homes. Appalled by the horrors, she was convinced that Jews needed a safe haven, and when I went into politics I promised to do my best to see that Britain didn't do anything that harmed Israelis. I'm now a member of the LFI executive.

Nonetheless, sometimes friends need to tell you when you've gone too far. This is one of those times. Israeli policy towards Gaza is wrong in principle, erratic in practice and now damaging to longer-term peace prospects.

We should accept that the position is hellishly difficult. Gaza is ruled by Hamas, an organisation that is in rebellion against the elected, internationally-recognised Palestinian leadership, denies Israel's right to exist and sponsors armed attacks on civilians. Moreover, the current fighting follows an explicit termination of the ceasefire by Hamas. If you end a ceasefire, shouldn't you expect to be attacked?

Up to a point, yes. If Israel launched air strikes against groups preparing to fire missiles, it would be entirely covered by international law on self-defence. If, during the Troubles, Ireland had tolerated missiles being launched from its territory against Belfast, we would have certainly felt entitled to hit back. The problem is that Israel's response consistently reaches beyond Hamas's leadership and terrorist groups and affects the entire civilian population. The current offensive is targeting Hamas, but entirely inevitably it is killing significant numbers of civilians as well – clearly more than the 14 killed by all the missiles fired at Israel over the last two years – and must be terrorising everyone living in the area. It is a wholly disproportionate response, as if we'd launched air raids on Dublin in response to outrages by IRA groups.

Nor is this the first example of the civilian population being made hostage to the sins of the leadership. The stranglehold imposed by the blockade of the territory turns the whole area into a quasi-prison camp, dependent for quite basic provisions on the goodwill of the Israeli government from week to week.

But perhaps this is realpolitik and it will make the region safer? Is there any sign of that? At some point the military operation will end. Failing a complete reoccupation of Gaza, Israel will still be sitting next to a neighbour with more reason than ever to be hostile, and it will join the Lebanon and earlier operations in the list of tactical successes that led exactly nowhere.

It is hard to avoid the impression that the operation is designed to strengthen the governing parties before the imminent Israeli election, and to weaken Hamas before Obama takes over. But what kind of impression is President Obama going to have as he weighs up American policy options? We owe it to our Israeli friends to be frank. They are going too far, and forfeiting support from quarters that they need, including Britain's. It is time to stop and think.

Nick Palmer is the Labour MP for Broxtowe and a member of the executive of Labour Friends of Israel. He is writing in a personal capacity.