A huge computer failure has caused chaos at the Department for Work and Pensions, according to reports.
Payment of existing benefits has not been affected, but staff have struggled to process new and amended claims, BBC News Online said.
The BBC said it had been told that about 80% of the DWP's network, used for millions of benefits and pension payments, crashed on Monday and is still not fully functional.
Technical experts from Microsoft and the computer firm EDS had been working around the clock to find the fault, which has left the staff having to communicate by fax because the e-mail system has broken down.
A DWP spokesman said the department expected remaining problems to be resolved on Friday.