The Prime Minister told his Israeli counterpart the move would “set back the prospects for peace in the region”, Downing Street said.
Mr Netanyahu has been eager to begin annexing West Bank territory in line with US president Donald Trump’s much-criticised plan for the Middle East.
However, the plan appears to be on hold as Israel awaits a green light from Washington and deals with a fresh coronavirus outbreak.
A Downing Street spokeswoman said last night: “The Prime Minister spoke to Benjamin Netanyahu, Prime Minister of Israel, this evening.
“The Prime Minister set out his concerns about plans to annex parts of the West Bank unilaterally and cautioned that this would set back the prospects for peace in the region. He reiterated his personal support for Israel and urged Prime Minister Netanyahu to return to negotiations with the Palestinians.
“The leaders also underlined their ongoing commitment to UK-Israel trade and discussed the global response to coronavirus, agreeing to continue working together to tackle the pandemic.” Mr Johnson last week warned the annexing would be illegal and would jeopardise relations in the Middle East.