Mobile operator Orange has increased the range of plans for its mobile broadband contracts, including one that costs under £5 per month.

The £4.89 tariff, which will be offered only to existing home and mobile Orange customers, is available on an 18-month contract and could be useful for mobile workers.

Orange said that users get a 500MB per month usage allowance, a free Huawei E160e USB dongle and download speeds of up to 3.6Mbit/s. The service is pitched at email and mobile web users.

Another new tariff may appeal to late-night users. 'Early Bird' offers unlimited mobile browsing between midnight and 9am in addition to data allowances already in place, which Orange said range between 1GB, 3GB and 10GB. These are offered on a less-restrictive 12-month contract starting at £13 per month.

"We are committed to building our mobile broadband portfolio so that it provides customers with a range of flexible solutions to suit the lifestyle they choose," said Asif Aziz, director of broadband and home at Orange.

"We also want to ensure that we reward existing Orange customers, and believe that, by offering them the cheapest pay monthly mobile broadband on the market, we really do offer great value for money."

Orange has also introduced a number of tools and services designed to help customers stay within data allowances. These range from software designed to warn users as they approach their threshold, to a monthly bill cap which Orange said would ensure that customers never go more than £40 over their usual spend.