Image caption Changes would not have an "excessive impact to transparency", Ms Grant said

The government is considering how to curb repetitive and overly expensive Freedom of Information requests, a justice minister has said.

Helen Grant said central government had received 47,000 requests in 2011, "at a cost of £8.5m in staff time alone", with local authorities "also affected".

"Disproportionate burdens" were being imposed by "what we call 'industrial users' of the act", she said.

But Plaid Cymru MP Elfyn Llwyd said she might be "over-stressing" her case.

In a debate in the Commons' secondary debating chamber, Westminster Hall, Ms Grant said: "Despite the many benefits that the act has brought, we cannot ignore concerns raised about the burdens that it imposes on public authorities.

"This is especially important in the current challenging and very difficult financial climate, and at a time when more Freedom of Information requests are made than ever before."

Transparency

She added: "Our research indicates that a very small number of requests contribute to a relatively large proportion of the cost of Freedom of Information. 8% of requests to central government cost more than £500 to answer, and make up a total of 32% of staff costs," she added.

At present, public authorities are entitled to refuse to answer a Freedom of Information request if they believe it will take them more than 18 hours' work to provide an answer.

The Commons justice committee has proposed cutting this limit to 16 hours, but Ms Grant said the government was considering "whether to go further on this".

"We will also consider other ways to reduce burdens in a fair and proportionate way, including addressing where one person, or a group of people, use the act to make unrelated requests to the same authority so frequently that it brings an inappropriate burden," she said.

"Whatever measures we may ultimately decide to take, we will have regard to the need to reduce burdens without an excessive impact to transparency."

'Zombie request'

Intervening in the minister's speech, Mr Llwyd said: "I don't believe that any local authority who gave evidence to us said that the costs were prohibitive upon their authority.

"Perhaps the honourable lady is over-stressing that aspect of it."

In a report published last July, the justice committee catalogued a string of requests it described as "frivolous".

Representatives of Leeds City Council told the committee they had received "a number of requests about ghost sightings and paranormal activity in its buildings".

A Cabinet Office official said his department had received a question about zombies, which had obliged one of his colleagues to "make sure that the part of the Cabinet Office that deals with contingencies does not actually have anything".

But the committee concluded: "We acknowledge the irritation experienced by public authorities which receive frivolous or trivial requests but, since these can normally be dealt with quickly at minimal cost, we do not recommend any change in the law in this area."