The grandfather of kidnapped Israeli soldier Gilad Shalit has sharply criticised Prime Minister Binyamin Netanyahu's effort to free his grandson, calling him the one obstacle to Sgt Shalit's freedom.

During a brief visit to London, Zvi Shalit, 85, admitted it was difficult to keep hope alive when nothing had been heard of Sgt Shalit since a short videotape was released by Hamas in 2009.

He said: "The family's state of mind is very, very bad. Our working formula is that Gilad is alive. But we have no proof. We have had no information for two years. And if the government had information, then they would say it."

Sgt Shalit, 24, will have spent five years in captivity in Gaza by June 25. He has been denied access to the Red Cross throughout his whole time as a hostage.

His grandfather, a British navy veteran, said Amnesty International had only just got in touch with Noam Shalit, Gilad's father, last week. But he added: "Even if they tried, they have no influence on Hamas, Hamas don't feel obliged to comply with human rights.

"The focus of lobbying should solely be Netanyahu. If he made up his mind, it could happen tomorrow. He doesn't need the government to answer the demands of Hamas, he can decide himself. I'm sure there would be a different outcome if the political situation was different. He has no compassion."

He was cautious about any new rumours that surface about a possible release deal. "There are some indication of things restarting but we have always been disappointed. There are always rumours."

The Israeli government takes the brunt of his anger. "I don't know the people who took Gilad. I don't expect anything from them. I expect something from the Prime Minister. But we don't want them to take military action, because then Hamas will just kill him. We only want a deal.

"Their argument is that releasing terrorists would be dangerous. It's irrelevant, there's no indication that it would be dangerous. Hamas wants to commit terrorism acts in Israel now, and they are unable to do it. We don't need to prove our strength. We have other means to do that. Not in these circumstances."

Mr Shalit was in London to visit his cousin, Hemda Garelick, and to speak at a Zionist Federation training day. The cousins spent Friday night with a couple Ms Garelick met outside Parliament, protesting against Sgt Shalit's captivity. She said: "People do care, these people are not Jewish, or pro-Israel or religious. But they said hearing about Gilad broke their heart."

She added: "Gilad was a quiet boy, introspective. It has been hard for the family to stand up and be the spokespeople for the campaign, it doesn't come naturally. But you acquire this strength because you have to do it. But it's very hard for Noam and Aviva [Gilad's parents]."

Mr Shalit stressed Britain's importance in putting pressure on the Israeli government to make a deal with Hamas. "I attribute to Britain a special importance in world affairs," he said.