Speaking about the allegations, Michael Dobbs said: "Emotionally, it was a tremendous shock, a huge blow to me."
But, he added: "No individual is greater than the show."
"Not even me, if I fell under a bus tomorrow, the thing will, should, must carry on."
"Thousands of people depend directly or indirectly on the show, so it's hugely important that it go on.
Lord Dobbs, who is a Conservative peer, wrote the original House of Cards books in the 1980s.
He went on to write the BBC adaptation of the show, which aired in 1990, and now serves as an executive producer on the Netflix series.
"It's not been the easiest few weeks, I must say, my world seems to have tilted on its axis somewhat," he told BBC Radio 4's Today programme.
"We'd only got to two episodes into the last season - so [there's been] a great deal of re-writing. The poor people have been sweating over their candles and quill pens.
"It's been really, truly difficult. What MRC - the production company - Netflix and the writers have done, I think has been truly superb."
He said that Spacey's co-star Robin Wright will continue in her role and become the central character in the plotline.
"Already, Robin Wright, had become an equal star. In fact, in many cases she was leading the plot. So, to that extent, it's been a relatively easy transition," he said.
Speaking about the viewing figures of the show's next season, Lord Dobbs said: "I think the next episode that comes out, which will be the first episode of the final season, will probably have the biggest global audience of any of the episodes of House of Cards. And it does already go all the way around the globe."
After a string of men came forward with allegations of sexual misconduct against Spacey, a representative for the actor said he was "taking the time necessary to seek evaluation and treatment".
Lord Dobbs said: "I'm going to say nothing about [Spacey] because I don't know. Other people will decide for themselves what was right or wrong.
"But it was about time that somebody in Hollywood set some standards for personal conduct."
The sixth season of House of Cards will resume production in 2018 confirmed Netflix's chief content officer on Monday.
Ted Sarandos said the final series would comprise eight episodes - each previous one had 13.
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