Security guards were forced to remove protesters who pitched a tent in the aisle of a Waitrose store and spent an hour urging shoppers not to buy Israeli goods.
The protest was organised by Brighton Jordan Valley Solidarity and its supporters included Simon Levin, one of the seven activists cleared last month of damaging an arms factory after successfully claiming they had acted to prevent Israeli "war crimes".
Staff called police after 10 protesters refused to move from the store in Western Road, Brighton.
They put up the tent and told shoppers the Israeli government was destroying Palestinian homes.
They also handed out leaflets which read: "Dear shopper, do you really want to buy stolen goods? Do you really want to buy goods from a country guilty of war crimes?"
They filled baskets with Israeli-made food to demonstrate to shoppers which ones to boycott.
A letter was also handed into the store on behalf of the group "to express our outrage at Waitrose continuing to stock large amounts of Israeli and illegal Israeli settlement goods for sale to the public. Considering how much more ethical Waitrose appears to be than most supermarkets, in the case of supporting the ethnic cleansing of Palestinians from their ancestral lands you are, disappointingly, the worst offender."
Police took more than an hour to arrive and "oversaw" the ejection by security guards.
Sam Barsam, of Hove Hebrew Congregation, said: "All boycotts are unfortunate, but this protest was really intimidating. We think this was a wake-up call, and we will be vigilant to see it is not repeated. The harassment against the shopper is unconscionable and smacks of discrimination against that small part of the population that wishes to buy Israeli and kosher produce."
A Waitrose spokeswoman said: "Relations with staff were cordial throughout. They asked the group to move on and, after initially refusing, they did so after police arrived."
Vivian Wineman, president of the Board of Deputies, said customers had complained to the store manager who were concerned about the safety of shopping there.
He added: "The manager has also expressed his concerns at the negative impact that these incidents may have on business.
"But we were thoroughly reassured that the episode was handled in the best manner possible under such difficult circumstances."