The director general of MI5 and the director of GCHQ have written to all chairmen of FTSE 350 companies asking them to take part in a "cyber governance health check", in a bid to raise awareness at the top of the corporate food chain and highlight internal vulnerabilities.

GCHQ and MI5 want both the chairman of each company and the chair of the company's audit committee to complete a questionnaire that aims to assess how well the big businesses handle issues such as protecting intellectual property and customer data, reports the Financial Times.

Results will be aggregated on an anonymous basis, so that companies can see how they compare to their peers.

The news comes in the same week that kitchenware retailer Lakeland revealed that it suffered a 'sophisticated and sustained' cyber attack, where hackers gained access to its encrypted databases via a Java software vulnerability.

The letter sent out to the FTSE 350 has been signed by David Willets, the science minister, as well as Andrew Parker of MI5 and Sir Iain Lobban of GCHQ. It states that the results will give them a "sense of how cyber-aware companies are, and what sort of risk assessment they have put in place".

It is expected the results will be published by November. However, this will be followed up by a detailed discussion with the company's audit firm about areas in which a company may be particularly vulnerable.

The security chiefs are hoping that the survey will be completed by the chairmen of the companies involved, rather than those already working with technology and data protection.

"By delegating the completion of the Tracker (e.g. to your chief information officer), your results may overlook existing internal vulnerabilities," states the letter.