ITV's shares fell 11.9p or 6 per cent to 179.1p, after the company reported that its channels took a 21.6 per cent share of viewing in the year to April 30, down from 23.4 per cent in the same period last year.
Mr Crozier, formerly chief executive at the Football Association and Royal Mail, said: "We continue to make progress with our strategy of growing and rebalancing the business in the UK and internationally."
He added: "While ITV Family share of viewing has been lower than expected so far this year we have confidence in our strong schedule to come, including the Football World Cup in June. ITV Encore - our first pay channel - is on track to launch in June, followed later in the year by ITVBe, our first new Free To Air Channel in almost a decade."
ITV shares broadcasting rights for the World Cup tournament in Brazil with the BBC. STV in Scotland will show every match that ITV screens.
ITV, home to shows including Coronation Street and Britain's Got Talent, said its first-quarter advertising was up just 2 per cent but it achieved a 19 per cent rise in April thanks to a late Easter. It is forecasting a 7 per cent year-on-year rise in advertising for May, with the World Cup expected to guide it to a 12 per cent to 15 per cent rise in advertising revenue in June. This is still shy of what some analysts had anticipated.
ITV said that total external revenue for the three months to March 31 rose 2 per cent to £585 million.
Revenue at its production unit fell 4 per cent in the quarter, which it attributed to the phasing of programme delivery.
ITV has been building up its production capabilities to reduce its reliance on advertising revenue, and last week bought US reality TV producer Leftfield Entertainment, maker of shows such as The Real Housewives of New Jersey, for up to $800m (£477m).
Mr Crozier said that production revenues are hit by the timing of programme deliveries.
But he said: "We are confident of delivering good revenue growth over the full year driven by the acquisitions we have made."
He said of the Leftfield purchase: "The acquisition makes ITV Studios the largest independent unscripted producer in the US and is a major step forward in our strategy of building an international content business.
"We are also investing in the organic growth of our international scripted business."
Keith Bowman, equity analyst at Hargreaves Lansdown Stockbrokers said: "Despite a relatively slow start, management remains confident for the full year. The coming Football World Cup is expected to boost advertising revenues, the group's push to acquire content and reduce its reliance on volatile advertising has taken a significant step forward."