The government has left open a back-door route that could allow it to introduce the controversial plan for a database of all electronic communications without any debate in parliament.

Ministers have refused to deny accusations that the government is using European legislation to bring in the proposals that were postponed after widespread criticism last year.

Last week, parliament officially rubber-stamped a statutory instrument requiring ISPs to retain all communications data for a year.

The measure was billed by the government as the transposition of the final part of the EU Data Retention Directive into law.

But shadow security minister Baroness Neville-Jones raised fears in the House of Lords yesterday that the legislation was a Trojan Horse for the government's Interception Modernisation Programme – the plan to build a database of all communications in the UK, including email, phone calls and web browsing.

"The government has not been able to satisfy these Benches that last week’s statutory instrument did not create a vehicle through which the Interception Modernisation Programme could be carried into practice without further primary legislation," she said.

"The draft Queen’s Speech led us to believe that primary legislation would be forthcoming and that the powers contained in the statutory instrument would be transposed in a Bill of primary legislation.

"Instead, the statutory instrument has been transposed separately, and against the background of the home secretary having cast doubt in a recent speech on the need for primary legislation."

Baroness Neville-Jones then asked Lord Bach, parliamentary under-secretary of state for justice, whether a prototype of a centralised database for communications data is under construction.

In response, Lord Bach failed to deny any of the accusations.

"We have not commented on reports of a central database for communications data and, I repeat, our plans will be outlined shortly in the consultation," he said.

The consultation document is expected to be published later this month, after home secretary Jacqui Smith was forced to delay plans for the Communications Data Bill that was originally intended to go before MPs in November last year.

Baroness Neville-Jones highlighted the Regulation of Investigatory Powers Act (RIPA) as a previous example where similar surveillance powers had been brought into law without debate in parliament.

When RIPA was passed, local authorities were not included in the list of public authorities that could access communications data. During the passage of the Bill the government gave assurances that such bodies would not be able to use the powers.

But in 2003 two orders were passed that gave a number of additional public authorities access to the data.

Home office minister Vernon Coaker later said the circumstances in which the assurances were given had changed.

“Clearly, if an assurance has been given you like to try and ensure that that assurance is maintained, but ... sometimes there are things that happen two, three, four, five, six years later ... despite the assurance that was made there is a need to change," he said at the time.