Insurers have warned against "distracting" the National Employment Savings Trust (NEST) from its original purpose by lifting government-imposed restrictions.
The Department for Work and Pensions' call for evidence on removing the annual contribution limit of £4,400 and transfer ban closed on Monday.
In response providers argued NEST could lose focus on its target market of low-earners and small companies if it is released from the constraints.
Legal & General pensions strategy director Adrian Boulding (pictured) said NEST could struggle to cope with the 30,000 firms employing 62-250 workers which reach their staging dates in April-July 2014.
Standard Life head of workplace strategy Jamie Jenkins argued NEST should first prove it has met the needs of its target market.
He said: "The market is already delivering a range of solutions for employers and NEST needs to operate effectively in the market to meet its public service obligation.
"However, we are still at the early stages of the auto-enrolment roll out and believe the removal of restrictions should only be considered once NEST has demonstrated it is meeting the needs of its target market. This includes enrolling the employees of smaller employers, which in the main won't happen for a few years."
Friends Life claimed the annual contribution limit has allowed NEST to maintain a product that fits with its target market.
In its submission, the insurer warned: "If the restriction on contribution levels were relaxed, leading to a larger number of higher paid individuals being included, we would anticipate significant investment in the NEST proposition to be required to meet the needs of more sophisticated investors demanding more choice with regard to investment options and options at retirement."
Friends Life said transfer restrictions should be removed mid-2014, while the contribution limit could also be lifted if it was found to restrict the choice of smaller employers by then.
Master trust provider B&CE, often seen as a competitor to NEST, said it is "supportive" of NEST.
However, director of customer solutions Jamie Fiveash said: "Its situation is different to most providers. It has a public service obligation but is also referenced by the regulators in communications and has access to substantial government funding at preferential rates. Therefore, it is sensible to ensure that there is some form of control over any provider in this position."
He added: "If these restrictions are deemed unsuitable, there needs to be clear evidence to demonstrate why as well as suggestions as to what rules should replace them. We have also not seen any evidence that a contribution cap is a barrier in serving its target market."
Fiveash said it is "too early" to discuss the suitability of the restrictions with thousands of employers still to choose a scheme, and said 2017 will be the right point to assess the impact of the restrictions.
However, Aviva said the restrictions were adding unnecessary complexity to employer's auto-enrolment decisions.
Aviva head of corporate benefits policy John Lawson said: "Pensions and auto-enrolment are complicated enough without adding in further barriers. People shun pensions because of this complexity and we should grasp every opportunity to make pensions as easy and customer-friendly as we can."
On Monday, a group including the TUC, Age UK, the Federation of Small Businesses and the British Chambers of Commerce wrote to pensions minister Steve Webb arguing there is an "urgent need" to the remove the restrictions.
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