Over a third of a £20m fund designed for blue/green infrastructure was not spent last year.
It comes amid severe financial pressures facing Stormont departments that have been worsened by the Covid-19 pandemic.
Blue/Green infrastructure refers to land and water spaces and is used in relation to urban planning aimed at improving the environment and promoting 'active travel'.
Of the £20m fund for blue/green infrastructure, £5m was spent on a Covid revitalisation programme across all councils, £2.4m went to greenway projects across three council areas, and £1.3m was spent on a pilot of electric minibuses for community transport.
Some £3.7m went towards foot and cycle ways, pop-up cycle lanes, crossings and social distancing measures, £150,000 for flood prevention schemes at Forth River and Belfast Castle, and £100,000 was given to Belfast City Council for the Belfast Bikes scheme.
A total of £54,000 was spent on electric vehicles to replace end-of-life petrol and diesel vehicles within the Department for Infrastructure's fleet and £53,000 went towards planting and greening schemes.
This means, of the £20m, only £12.75m was spent — some 64% of the pot.
Infrastructure Minister Nichola Mallon said: "I would like to have delivered full spend against this budget, and my officials have canvassed widely for projects, but spending often requires complex preliminary work to be sufficiently advanced in what is an innovative area.
"I am also keen to support Council Greenway proposals, but it is important that councils work with stakeholders to develop their proposals to the point that they are ready to be built. The outturn is substantial and this, together with my commitment to a £20m budget for this year, will continue to build momentum for this kind of investment.
"I recently announced £2.5m funding for Greenways this financial year and I am keen to make more allocations to schemes that are in a position to start construction this year."
Alliance infrastructure spokesperson Andrew Muir said Ms Mallon needs to more to fund active travel.
"Spending on cycling infrastructure in Northern Ireland remains totally insufficient. Last year, the Department spent around £3 per person on cycling infrastructure, which is nowhere near good enough. As part of the Alliance Party’s Green New Deal, we would raise that to £10 per head by 2025 at the latest," he said.
"Figures out last week show that the rates of walking, cycling and public transport usage in Northern Ireland haven’t budged over the past ten years. If we’re serious about modal shift, the Minister needs to start investing more of her budget to active travel."
Last November the charity Sustrans said Northern Ireland has the lowest level of official investment in walking and cycling in the UK.