The Green Party’s only MP has been criticised after she backed campaigners calling for a boycott of an Israeli eco-friendly company.

Caroline Lucas has lobbied Southern Water over its deal with Arad Technologies, one of the world’s leading producers of hi-tech water meters.

Southern Water last month installed a non-Israeli-made meter at the home of Brighton activist Caroline O’Reilly after she refused to accept an Arad system.

Around a dozen boycotters have lobbied Southern over the issue, and have been supported by Ms Lucas.

Zionist Federation chairman Paul Charney wrote to Ms Lucas on Monday and asked her to reconsider her “misguided call for a boycott”.

Working with UK Lawyers for Israel, the ZF has also written to nine other MPs whose constituencies are covered by Southern Water, advising them that a boycott of Arad could form discrimination by nationality and be illegal.

In his letter to Ms Lucas, Mr Charney wrote: “Arad may supply products which are used by Israelis in the West Bank. So do Microsoft and lots of other companies — you are not demanding that Southern Water (or anyone else) stop purchasing Microsoft products. Your approach clearly discriminates against Arad on the basis of nationality.

“The allegation that Israel deliberately starves Palestinians of water to push them off the land is completely false.”

Ms Lucas wrote to a constituent at the end of July to say her opposition to Arad was “not because they are an Israeli company, but because of their involvement in human rights abuses”.

The Brighton Pavilion MP claimed the company was robbing Palestinians in the West Bank and Gaza of water “as a way to push them off the land… so that their land can be expropriated by settlements”.

Ms Lucas concluded: “Water conservation work by Southern Water is incredibly important but, as Caroline O’Reilly’s case has demonstrated, it doesn’t have to be at the expense of Palestinian human rights —the company could be using an alternative supplier, as I have called on them to consider as standard policy.”

Southern Water said last month it had installed nearly 300,000 Arad meters, had another 200,000 to install, and had no intention of boycotting the company.

Arad’s Rami Ziv said the company did not engage in political debate.