A number of MPs have called for the UK to reassess the support being given to Israel after its forces killed seven aid workers in Gaza this week.
Oliver Dowden said Israel was conducting a “legitimate” war.
But he suggested the UK would stop supplying Israel arms if it was found to be in breach of international law.
Meanwhile, Labour is calling on Foreign Secretary Lord David Cameron to face questions from MPs on the legal advice he has received on the issue.
Israel faced criticism from allies this week after an IDF unit attacked a convoy of World Central Kitchen (WCK) vehicles from the air, killing seven people including three British military veterans.
When asked on the BBC’s Sunday With Laura Kuenssberg whether Israel was acting within the law, the deputy prime minister said legal advice on UK arms sales had not changed.
Israel was “still facing this existential threat from Hamas” and was “prosecuting a legitimate war of self-defence”, Mr Dowden said.
“The key thing is, ‘is it legitimate, can we lawfully sell arms to Israel?’ and yes, that is the case and on that basis… that position has not changed,” he said.
“We will of course act in accordance with our obligations under law in respect of arms sales.”
Mr Dowden was asked about comments from the Conservative chair of the Foreign Affairs Select Committee, Alicia Kearns, who said the government had received advice which said Israel had broken international humanitarian law.
The deputy PM did not directly deny the claims, saying the government would not publish legal advice it had received and that he was “cautious about getting into individual details”.
Mr Dowden said the UK had “specific concerns” about Israel’s conduct over access for aid workers and civilian deaths and “Israel has engaged with those”.
He also hit out at “the kind of relish” he said some were taking in criticising Israel, saying they were “holding Israel to standards we wouldn’t remotely hold other countries to”.
He said it was “all too easy” for the world to forget “the horrors of six months ago”, when about 1,200 people were killed and 253 hostages seized.
About 129 hostages remain unaccounted for, with at least 34 presumed dead.
Since then, 33,137 people have been killed in Gaza, with more than 75,815 injured, the Hamas-run health ministry says.
Labour’s shadow foreign secretary David Lammy has written to the government calling on the foreign secretary, who as a peer would normally be questioned in the House of Lords, to come to the House of Commons so MPs can question him over the legal advice on UK arms exports to Israel.
Mr Lammy said he had “very real concerns that our obligations according to international humanitarian law… might have been breached”.
“It’s hugely important that the UK is not complicit in a breach of international law,” he said, adding: “I remain concerned until I have seen that advice.”
There are ethical as well as legal questions, said Lord Mark Sedwill, who was the UK’s top civil servant before leaving to become a non-executive director at BAE Systems, which is linked to arms sales in Israel.
“There’s a separate question,” he said. “Even if it’s lawful, is it right to continue these arms sales?
“Can they be used to extract some kind of leverage over Israel about the way they’re conducting this campaign?
“David Cameron’s remarks about our support being not unconditional I think hints that he is thinking in those terms.”