The Marine Scotland study found that beach and coast users are the worst culprits for litter and that plastics have become the biggest threat to the environment and the coastal and maritime economy, which is worth at least £2.2 billion a year and supports 50,000 jobs not including the oil industry.
Undersea and coastal wildlife tourism, sailing and sea angling are among the key leisure activities being hit by litter including plastic bags, food containers, fishing gear and debris from ships.
The lack of improvement in levels of marine litter is a key stumbling block for the Scottish Government's green ambitions and its Zero Waste Plan.
The report said marine litter threatens targets including reducing waste significantly by 2020 and may "impact upon Scotland's Strategic Objectives, most notably the drive to become a Greener, Wealthier and Fairer, Safer and Stronger and Healthier Scotland".
The impact on tourism is clear with the report showing that 85% of tourists and residents would not visit a beach with more than two items of litter per metre.
The report found beach users and recreational tourists account for 37% of beach litter, sewage related debris 20.5%, 8.9% fishing and 1.7% shipping.
The implications for the Scottish economy are "highly significant", the report says, from the cost of cleaning beaches, loss of tourism revenue and the economic cost of direct impacts of damaged gear or lost commercial catches in fisheries.
The Marine Conservation Society said the most worrying aspect is that plastic makes up 61.5% of the waste, up from 51.8% in 1996.
Damage caused by waste costs Scottish fisheries £10m a year and it is estimated to cost every crofter in the Shetlands £840 a year.
As well as having a devastating effect on the environment, marine litter is hitting marine wildlife tourism such as diving which is worth £15m a year and sustains 650 jobs, coastal wildlife tourism is worth £24m with 1000 jobs, and sea angling is worth £70m and supporting 3150.
The report says: "The problems and threats caused directly or indirectly by marine litter are extensive, including environmental, social and economic impacts. Marine litter has a substantial impact upon the economy.
"It is clear marine and coastal litter can impact and deteriorate a range of natural functions that provide on-going social and economic benefits.
"The approximate economic cost of the marine litter problem in Scotland is £16.8m per annum. However, this figure is underestimated."
The Marine Conservation Society echoed concerns that plastics caused the environment and the taxpayer dearly.
Anne Saunders, Scottish projects officer for the Marine Conservation Society, said: "Marine litter comes from many sources, of which most are preventable.
"For example, no sanitary items should be flushed down the toilet.
"Accidental spills of materials can occur if industry practices and procedures are not robust or are not implemented properly.
"The cost to local authorities of cleaning litter from beaches runs into millions of pounds per annum, which again is passed on to the public through council tax bills. It is possible to reduce many of these impacts by industry being more environmentally aware and tightening up procedures.
"The public can easily do its bit by not flushing sanitary items down the toilet and not dropping litter."
Plastic bags are the subject of a Holyrood consultation under the Zero Waste Plan with a tax under consideration, which the Scottish Government believes will help the environment and the economy.