Ministers have been strongly criticised for including a valuable database containing millions of postcodes and postal addresses in the sale of the Royal Mail to boost the share price.
The Commons Public Administration Committee said the Postcode Address File (PAF) should have been retained as a "national asset" freely available to all for the widest benefit of the economy.
It said the PAF's disposal to the private sector for "short-term gain" in last year's Royal Mail flotation was an "unacceptable and unnecessary consequence of privatisation" which could hold back economic innovation and growth.
Committee chairman Bernard Jenkin said: "The sale of the PAF with the Royal Mail was a mistake. Public access to public sector data must never be sold or given away again."
The PAF contains all known Royal Mail delivery points in the UK with 1.8 million postcodes and 28 million postal addresses.
In its report, the committee said the database - which had been expensive to collect and collate into usable form - was of "huge direct value" to the economy.
However it expressed concern about the credibility of assurances that had been given regarding continued access for small businesses and others, now that it was in private hands.
"The Postcode Address File was included in the sale to boost the Royal Mail share price at flotation. This takes an immediate but narrow view of the value of such data sets," it said.
"The PAF should have been retained as a public data set, as a national asset, available free to all, for the benefit of the public and for the widest benefit of the UK economy.
"Its disposal for a short-term gain will impede economic innovation and growth. This was an unacceptable and unnecessary consequence of privatisation."
The committee broadly welcomed the Government's commitment to opening up official data to the public.
However, it said the promised "army of armchair auditors" - members of the public who, ministers had predicted, would seize on the data to hold the public sector to account - had so far failed to materialise.
"There is no sign of the promised emergence of an army of armchair auditors," it said.
"There is little or no evidence that the Cabinet Office is succeeding in encouraging greater public engagement in using data to hold the public sector to account."
The Department for Business, Innovation and Skills defended the inclusion of the PAF in the Royal Mail flotation.
"The Postcode Address File was included in the sale of Royal Mail because it is an integral part of its operations, not to boost the price," a spokesman said.
"The Government also recognises the importance of access to the data for innovation. While ensuring that PAF remains in Royal Mail's ownership, we are confident that we have secured benefits for data users including free look-ups that will open up new opportunities for growth."
The Royal Mail said in a statement that it took its responsibilities and obligations in relation to the PAF very seriously and would be bringing forward its final proposals to simplify the licence "very soon".
"Royal Mail recognises the importance that PAF plays as a vital dataset supporting and sustaining key parts of the UK economy and we are committed to its widespread availability at a fair price," it said.
"The proposal, which we expect to finalise very soon, aims to widen take up, encourage greater use of PAF, and meet the current and future needs of users, solutions providers and developers of PAF-based products in today's marketplace."