Insurers insist NEST should retain its current transfer ban and contribution cap ahead of the roll out of auto-enrolment.
This morning MPs recommended the two restrictions - put in place to limit NEST's competition with the wider pensions market - should be removed.
However, the Association of British Insurers (ABI) said making changes before its launch would be a mistake.
Director of life, savings and protection Stephen Gay (pictured) said: "NEST was designed - with the full support of the pensions industry - to help those on low incomes.
"With auto-enrolment beginning this year, it should focus on doing that, rather than competing for higher paid customers who already have plenty of choice."
Legal & General pensions strategy director Adrian Boulding - one of the trio behind the Making Automatic Enrolment Work review - agreed the restrictions should remain in place.
He said: "There is a strong social need for a national saving scheme (NEST) among the low paid and the hitherto un-pensioned, the majority of whom may be working for small employers. These restrictions keep NEST tightly focussed on the areas where the nation needs it.
"Removing the restrictions before the scheduled review in 2017 would risk NEST becoming distracted to the detriment of the very consumers it was created for. "
Confederation of British Industry (CBI) also cautioned against making further changes ahead of auto-enrolment's roll out.
Director for employment policy Neil Carberry said: "It's disappointing that the committee has not focussed on the real reason why NEST may be struggling to compete with low-cost private sector competitors, which is its high and complex charging regime."
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