Lycamobile has given Conservatives more than £300,000 in last nine months, but has paid no coporation tax for three years

A mobile phone company that has paid no corporation tax for three years has become the Conservatives' most generous corporate donor after giving more than £300,000 over the last nine months, new figures show.

Lycamobile, an £88m company based in Canary Wharf, gave more than £130,000 in donations between January and March this year, the latest Electoral Commission records show. This was on top of previous donations at the end of last year.

Insiders from the company have confirmed that most of the last quarter's money was spent on Boris Johnson's successful campaign to be re-elected as London mayor. Johnson has publicly praised Lycamobile's sim cards and mobile telephone technology, and the company's founder, Subaskaran Allirajah, has attended Tory party fundraising events with David Cameron.

According to the Electoral Commission figures, Lycamobile gave the Tories £34,350 cash and £97,262 in "non-cash sponsorship" between January and March.

The latter is believed to be the use of the company's offices for telephone canvassing. The Back Boris website shows that the campaign team called for volunteers to attend Lycamobile's offices on at least five occasions..

Johnson lavished praise on Lycamobile at the company's fifth birthday last July, telling journalists it was as dynamic as London itself and joking that its technology was "unhackable".

Executives from the company also attended Ken Livingstone's fundraising events and discussed donating £100,000, but no money was handed over.

The latest available figures show the company did not pay any tax between 2008 and 2010, despite generating a turnover of between £47m and £88m.

Lycamobile's recent donations were accepted by the Tories on 19 March, while the company was under threat of being struck off by Companies House for failing to register its annual accounts. The move was suspended five days later following an intervention by the company.

The accounts are nearly two years late, but were filed last week, according to a spokesman. They have not yet appeared on the Companies House website. Lycamobile has said it did not pay taxes because it was "growing the business" and therefore had not generated taxable income.

A spokesman said the company had paid all taxes due. The delay in publishing this year's accounts was, he said, a result of a "very thorough" audit by Ernst & Young. The company said it had generated and paid taxable receipts in the UK for more than £54m in VAT as well as national insurance and PAYE contributions.

"We are pleased at the progress we have made both in gaining market share leadership and in terms of profitability, which will be reflected in the accounts. These tax losses are able to be carried forward and offset against future taxable profits," the spokesman said.

Lycamobile is a mobile virtual network operator (MVNO). It was launched in 2005 and has companies in Australia, Belgium, Denmark, France, Germany, Italy, Netherlands, Norway, Poland, Spain, Sweden, Switzerland and the UK – and recently launched in Australia. It is part of the Lyca Group of companies, which has around 60 different entities in Europe and Asia.

The Australian Communications and Media Authority (ACMA) issued Lycamobile with a formal warning earlier this month for breaching the country's Telecommunications Act. The authority found that the pay-as-you-go company had failed to provide accurate customer records, which contain listed and unlisted public phone numbers used for emergency calls and law enforcement.

Allirajah controls another company, Lycatel, which sells cheap international phone cards. Between 2008 and 2010 Lycatel had a turnover of £260m, but again paid no tax.

Cheap international calls are big business, as low-paid migrant workers look for the best rates to phone home.

In July, Lycamobile issued an advertisement claiming: "Call India, Pakistan and Bangladesh landlines for only 1p a minute." The Advertising Standards Authority banned the ad for playing down the fact that rates increase after 15 minutes. In February, the company faced censure for issuing leaflets offering "1/2p a minute" international calls.